THE PREVENTION OF EPIDEMIC INFLUENZA WITH SPECIAL REFERENCE TO VACCINE PROPHYLAXIS
BySamuel R. Haythorn, M. D.
BySamuel R. Haythorn, M. D.
BySamuel R. Haythorn, M. D.
In developing practical measures for the prevention or control of influenza epidemics, preventive medicine faces one of the most difficult problems of modern times. By means of quarantine, protective vaccination and instructions in personal hygiene many of the diseases which formerly ravaged the world have been brought under control. At first glance it would seem to be a simple matter to apply the principles which we have found successful against these diseases to influenza and let it go at that, but in the recent epidemic many of the formerly successful measures were tried and found to be either inefficient, inapplicable, or at least of doubtful value.
During the pandemic there was little time to think collectedly, and no time to analyze procedures, and even now it is far from easy to determine what things were done wisely and what things were of no practical value. There exists the greatest difference of opinion as to what measures should again be used when the need arises, and what ones should be discarded. For instance, there are confirmed exponents of prophylactic vaccines, and equally able men who are convinced of their uselessness; enthusiastic advocates of the face mask, and almost as many objectors; those who would close schools, churches, theatres, etc., and those who claim that such measures serve only to prolong the epidemic. One naval officer is said to have stated that he had accumulated figures either to prove or to disprove the usefulness of any preventive measure yet recommended. There is, in short, a chaos of opinions with followers who vary from the one extreme of believing there is “virtue in all things” to those of the other extreme who state that every susceptible person develops thedisease in the degree of his susceptibility, regardless of any and all preventive measures used. While there remain so many points on which definite, concrete knowledge is lacking, and so much controversy over the relative value of various measures, this paper can do little more than state the facts and discuss their bearing on prevention as impartially as possible.
Great progress has been made in controlling contagious diseases in recent years—a fact which can be easily verified by anyone who will compare the sick reports of the Great World War with those of any war previous to the beginning of the present century. The diseases which have been most easily controlled have been those against which prophylactic vaccines or prophylactic sera have been developed. Smallpox, dysentery and typhoid fever have lent themselves readily to control by protective vaccination, while reliable temporary immunity can be afforded by the administration of sera for protection against diphtheria and tetanus. These are by no means all, but are probably the most striking illustrations; and with such examples before us, the greatest hope for the prevention of influenza apparently lies in the development of a prophylactic vaccine against it.
The name vaccine came from “vacca,” or cow, and was originally applied by Jenner (1796) to the virus taken from cowpox pustules for prophylactic inoculation against smallpox. It has come to be loosely applied to all forms of preventive inoculations except sera. We have, therefore, a variety of vaccines which differ in their nature and method of preparation. Some are produced by growing the virus in insusceptible animals, some are composed of attenuated viruses, and most common of all are the bacterial vaccines, sometimes called “bacterins,” which are prepared from killed cultures of bacteria. Sera are used in prophylaxis, as well as treatment, and are made by bleeding and separating off the serum from animals which have been immunized against the cause of the disease in question. Sera and vaccines are wholly different products, and the distinction should be made in discussing them, although there is a common tendency, particularly among lay writers, to use the words interchangeably.Smallpox is the classical example of a disease which can be completely controlled by universal vaccination. The parasite causing smallpox has never been certainly demonstrated, but over a century ago Jenner showed that cowpox, a localized, non-fatal disease, protected against smallpox. Modern methods have proven that a cow inoculated with smallpox virus develops cowpox, and that thereafter the virus loses its power to produce smallpox when it is returned to man. Instead, it causes a local pustule, and confers immunity to smallpox over a considerable length of time. Rabies is another example in which the exact cause of the disease is still in doubt, and in which a protective vaccine has proven of great value. Rabies vaccine was developed by Pasteur, and is prepared by drying the spinal cords of rabbits that have been killed by a highly virulent rabies virus. Typhoid, dysentery, pneumonia and several other diseases of known etiology have been more or less controlled by the use of vaccines made from their respective bacterial causes. These vaccines are of the “killed bacteria” type of vaccines, and credit for their application to human disease belongs to Sir Almroth Wright (1896). The preparation of bacterial vaccines is very simple. Bacteria which are known to cause a certain disease are isolated in pure culture, grown on artificial media, killed either by chemicals or heat, standardized either by counting, or drying and weighing, and suspended in salt solution for subcutaneous injection. Salt suspension vaccines are usually given in three or four increasing doses, about one week apart. Le Moignic and Pinoy (58) first elaborated a lipovaccine for triple typhoid vaccination, which was used extensively in France during the war. Whitmore, Fennel and Peterson have recently also advised the drying of killed bacteria and the suspension of them in oil. This method makes it possible to give a single massive dose of bacteria which is sufficiently large to completely immunize the individual against the disease, and which prolongs the immunizing period by allowing slow absorption over a period of several weeks. These vaccines are called lipovaccines, have been adopted in the United States Army as the standard typhoid vaccine, and promise in time to supersede the salt suspensions entirely from a commercial standpoint. Many other modifications in the preparation of bacterial vaccines have been advised, notably the class known as sensitized vaccines. These are prepared by incubatingbacterial vaccines for a time with the serum taken from animals already immunized against them. The serum apparently absorbs many of the toxic substances, and permits the injection of more efficient doses. Besredka advised the use of living cultures which had been incubated with immune sera, on the basis that vaccines so prepared were very active and non-toxic. The sensitizing treatment, however, does not stop the growing powers of the bacteria, and vaccines of the Besredka type are generally considered dangerous and so are little used. Sensitized killed bacterial vaccines, on the other hand, are quite popular.
When a sufficiently large dose of vaccine is given to an individual there is usually a transient rise in temperature for from 12 to 48 hours; the local focus of injection becomes sore and inflamed, and a white count often shows an actual increase in the number of polymorphonuclear leucocytes in the general circulation. A series of doses are usually given. If after a few days blood is withdrawn from the patient and immuniological tests made, it will generally be found that the patient’s leucocytes take up bacteria, and particularly the type of bacteria of which the vaccine was composed, more readily and in greater numbers than the leucocytes of the ordinary individual. Wright and Douglas (52) and Neufeld and Rimpau (53) have shown that this effect of increased phagocytosis is brought about by the vaccine through the production of substances which act specifically on the bacteria and render them more susceptible to inclusion within the white cells. These substances belong to the group of antibodies, and are known as “opsonins” or “bacteriotropins,” and are specific for any given bacteria. Moreover, the serum of the patient will, as a rule, be found to have developed the faculty of agglutinating and bacteriolysing suspensions of the specific organism injected and of fixing complement in the presence of an antigen prepared from that organism. In animal work it has been possible to go still farther, for it can be shown that the resistance of the animal can be raised until it is no longer possible to kill it with the same dose which is found to be fatal for the unimmunized animals. Not only has animal work made it possible to determine the protective powers of vaccines, but it has also served to show the specific nature of the protective power and the relative extent to which “group” or “crossed” protection can be conferred by vaccinating with closely alliedorganisms—as, for instance, paratyphoid bacilli in typhoid fever. The non-toxic nature of vaccines is also determined by animal experiment before such preparations are injected into humans.
The most successful prophylactic bacterial vaccine which has been developed so far is that for typhoid fever. A comparison of the occurrence of typhoid fever in the United States Army before and since the use of anti-typhoid vaccine is all that need be cited to convince one of its value. At the time of the Spanish War there was no vaccination against typhoid fever, and there were 20,738 cases, with 1,580 deaths, among 107,973 men who remained in the camps in the United States during the war (54).
During the summer of 1911, the maneuver division of the United States Army, having 12,801 men, all of whom had been vaccinated against typhoid fever, were stationed at San Antonio, Texas. Two cases of typhoid fever developed among them, and neither case died. Among the civilian population of the city, living under usual conditions during the same time, there were 49 cases of typhoid fever, with 19 deaths. Since 1912, typhoid vaccination has been compulsory in the United States Army, and the largest epidemic of typhoid fever which I have found reported so far during the late war was that at Camp Greene (55), Charlotte, N. C., where 18 cases developed. Only 12 of these men had received the complete series of immunizing doses. For a complete discussion of the value of typhoid vaccine the interested reader is referred to Gay’s Monograph (56) on typhoid fever.
The hope of finding an early solution to the vaccine problem in influenza appeared to be in the development of a prophylactic “bacterial vaccine” similar to that which proved so efficient for typhoid. In his discussion of the vaccine problem in pneumonia, Fennel pointed out that, theoretically, any disease of microbic origin in which spontaneous recovery is at all possible should yield to specific prophylactic measures. The difficulty, however, of preparing a bacterial vaccine for influenza comparable to that for typhoid fever is that the unquestioned cause of influenza has yet to be determined. The probable cause of influenza is the Pfeiffer bacillus, but its relationship has not been proven beyond question. On the other hand, the innocence has likewise not been proven, as Dr. Holman in his article of this series has ably shown.It is not my intention to go deeply into the question of etiology, but simply to bring out a few points whicha prioriseemed to indicate that the reasonable solution of vaccine prophylaxis was in the preparation of a pure Pfeiffer bacillus suspension.
The experiments in man lead to very surprising results. Rosenau, Keegan, Goldberger and Lake, at Gallops Island, Boston, Mass., (1) inoculated volunteers with pure culture of B. Pfeiffer, with secretions of the upper air passages and with blood from typical cases of influenza. Sixteen men, of whom 13 were supposedly non-immune, had Pfeiffer bacilli installed into their nasal passages, and none of them developed the disease. Secretions filtered and unfiltered also gave negative results. Contact with well-developed early cases also failed. McCoy and Richey (1a) conducted similar experiments in San Francisco, with negative results. The men of the latter group had been vaccinated with a mixed streptococcic vaccine, which may have played some part. Had the experiments with the Pfeiffer bacillus been negative and the other experiments positive, they would have shown that the bacillus of Pfeiffer was not the cause of influenza; but since all attempts were negative, it merely brought out the fact that there had been a change, due probably to some immune factor, which seemed to have acted alike on the Pfeiffer bacillus and all other types of virus present, and to have made them all innocuous. These experiments still leave the cause of influenza in question.
Those who are opposed to the Pfeiffer bacillus being the cause of influenza in its epidemic form base their position on the points that the common finding of the bacillus might be accounted for on the grounds of its being a secondary rather than a primary invader; that while it is not so common at ordinary times, it does occur with other organisms in whooping cough and sometimes in chronic diseases of the air passages, and that the rules of Koch have not been complied with in that the organism has not been found in every case of the disease; that where it has been grown in pure culture and inoculated into man and animals, it has either produced no disease, or the lesions which followed have not been typical of epidemic influenza. On the side of those who believe that the Pfeiffer bacillus is the chief cause, or, at any rate, that it is partly responsible for epidemic influenza, are the facts of its fairly constant presence in the purulent bronchial secretion of patients suffering from epidemic influenza;its relatively uncommon occurrence at other times; its known pathogenicity in occasional cases of meningitis, and in the inflammation of the bony sinuses of the head and face; the relative immunity of nearly all common laboratory animals and the fact that the attempts to transfer epidemic influenza from man to man failed not only when Pfeiffer bacilli were used, but also when direct contact and direct coughing by the patient into the face of the volunteer were tried. The argument that many cantonment laboratories failed to find the organisms loses weight when we find that the percentage of positives increased where the material examined was removed directly from the lungs at autopsy, where special cultural methods were in use and where the laboratory personnel was large enough to devote a sufficient amount of time to each individual culture. All of these points indicate that the organism was overlooked in a great many instances. In our laboratory we found the examination of sputa very unsatisfactory because of the great amount of contamination, and because the bacillus seemed to lose its ability to grow after a relatively short time in the sputum in vitro. Moreover, I am convinced that the bacillus changes its morphology to such an extent under varying conditions as to make it impossible of identification when present among other organisms in sputum smears. The failure of animal inoculations is also not conclusive evidence against the Pfeiffer organism, because guinea pigs, rats and mice have a natural immunity for them. Rabbits are only slightly susceptible, and then only to intravenous injections. The mixture of the Pfeiffer bacillus with any one of several other pathogenic organisms will increase the pathogenicity of both. Monkeys inoculated intracranially develop a typical Pfeiffer bacillus meningitis.
Whatever the ultimate outcome of the investigations as to the parasitic cause of epidemic influenza, the Pfeiffer bacillus was the generally accepted cause at the beginning of the 1918 epidemic, though it was at once realized that most of the deaths were due to complicating pneumonias and to secondary infections with other organisms. Under the circumstances, one of two courses was open: (a) the acceptance of the Pfeiffer bacillus as the presumptive cause of influenza and the preparation of a specific prophylactic vaccine against infections with that organism; or (b) the use of a mixed bacterial vaccine containing thecommon and most deadly secondary infecting organisms, designed to increase the patient’s general resistance by decreasing his susceptibility to the allied, collateral and secondary infecting agents. Attempts were made along both lines, with more or less unsatisfactory results.
By a specific prophylactic vaccine for any given disease, we mean a material which when inoculated into an individual will actively protect that individual against the given disease. In infectious diseases, the immunizing material is usually of microparasitic origin (in contrast to desensitizing substances used in pollen diseases and those due to unusual sensitiveness to foreign proteins), and is specific only for the disease caused by the microparasite from which the material was prepared. With the knowledge in hand during the epidemic, the logical plan seemed to be to prepare a pure Pfeiffer bacillus vaccine, the object of which was to eliminate primary infection with that organism and thus prevent the secondary invaders from obtaining a fertile soil.
While specific Pfeiffer bacillus vaccines had been tried in treatment, the field was a comparatively new one so far as prevention was concerned. Many of the biological products companies had so-called influenza vaccines on the market for treatment purposes, and many of these contained Pfeiffer bacilli. A few preparations of pure strains of the bacilli were also available, but I was unable to find any records of their use for prophylaxis. Lacy (2) reported two cases of sinusitis treated with autogenous vaccines made from pure Pfeiffer strains—one patient improved rapidly and the other showed no change. Investigation of several of the other references on influenza vaccines showed that mixed vaccines had been used in each instance. The work of Flexner and Wolstein (3, 4 and 5) indicated that active immunizing substances could be prepared from the Pfeiffer bacillus, although they worked with serum instead of vaccines. They prepared an anti-influenza-meningitis serum by immunizing goats and horses. These sera cured monkeys of experimentally produced influenzal meningitis. The sera showed agglutinins and bacteriotropins for Pfeiffer bacilli, as well as positive fixation tests in dilutions of 1 in 100, but they contained no lysins. The serum was offeredfor intradural use in treating influenzal meningitis, but was found to have no value when used in human cases.
The first references which we have found on the use of pure Pfeiffer bacillus vaccines for the prevention of epidemic influenza were those of Leary (6), (7), and of Rosenau (8). Shortly after the appearance of the first influenza cases in Boston, Leary used a vaccine prepared from several strains of Pfeiffer bacilli both for the treatment of influenza and for its prevention. The vaccine for the latter purpose was given to medical students and nurses, and the first results were apparently very encouraging. Continued use has not been convincing. Barnes (9) reported an attempt to protect the employees and patients of an institution near Woonsocket. On October 9 a case of influenza developed in the female ward, and was followed five days later by another. On October 22 the disease appeared in the male ward, and the same day 172 employees and patients were given their first inoculation with Leary’s vaccine. Doses of 400, 800 and 1,200 million bacilli were given at 24–hour intervals. All persons who had developed influenza before the three doses had been completed were excluded from the computation of the disease incidence, which was found to be 20 per cent. both among vaccinated and unvaccinated individuals. The mortality rate was 16 per cent. for the 25 cases among the vaccinated, and 15.8 per cent. among 57 unvaccinated patients. The result failed to show any protective qualities for the vaccine.
The best controlled vaccine experiment in which Leary’s vaccine was used was that reported by Hinton and Kane (10), and was carried out at the Monson State Hospital for epileptics. The hospital had a population of 979 inmates, ranging from 4 years of age to senility; of these 461 were vaccinated and 518 were not. Vaccination was begun on October 6, and three doses of 400, 800 and 1,200 million were given at 24–hour intervals. The first case of influenza developed a few hours after vaccination was completed, but there were no more cases before October 12, when five cases developed. The table shows the result of the work, and that the vaccine failed to protect.
Attempts to protect by the use of Leary’s influenza vaccine were made in 11 other Massachusetts institutions, but the results cannot be used to compare the incidence and mortality rates between the vaccinated and unvaccinated, because the epidemic was either on the wane, or at least well advanced when the vaccinations were begun. The reports are of great interest in showing the large number of vaccinations which failed to protect.
In the Taunton State Hospital about 800 were vaccinated, and among them there were 81 cases of influenza and 17 deaths from pneumonia, even though the epidemic was on the wane when vaccinations were begun.
In the Gardner State Colony 834 were vaccinated after the peak of the epidemic had passed. This number included all but 15 of the inmates who had not contracted influenza up to that time. Out of this group, 62 vaccinated individuals developed the disease.
At the Massachusetts School for Feeble-Minded 457 inmates were selected for vaccination and controls. Of the 234 vaccinated, 56 developed influenza. Of the 223 unvaccinated, 185 developed influenza, with 16 pneumonias and 12 deaths. The vaccinated group, however, were a more vigorous group of individuals to begin with, and represented a higher mental grade than the unvaccinated group, so that the evidence was considered of questionable value.
At the Wrentham State School the influenza epidemic was well under way before vaccinations were begun, and hence the susceptible individuals were in a large part either affected or infected with the disease. Of 1,198 unvaccinated persons, 758 developed influenza, giving a morbidity rate of 63 per cent. Of 128 vaccinated, 13 developed influenza and 1 died. Physicians in this institution believe that the vaccinated were not as ill as the unvaccinated patients.
In the Medfield State Hospital, having a total population of 1,940,421 cases of influenza, with 63 deaths, had occurred before vaccinations were begun. Of the remaining unattacked inmates 902 were vaccinated. After the completion of vaccination one new case appeared among the unvaccinated, and there were none among the vaccinated.
At the North Hampton State Hospital there were 9 cases of influenza, 4 of whom died, among 444 unvaccinated individuals, and 9 cases, with 1 death, among 563 vaccinated patients.
Among 506 patients vaccinated at the Westborough State Hospital there developed 15 cases of influenza, 2 of which terminated fatally. Of the 415 unvaccinated controls, 25 developed influenza and there were no deaths. At the time vaccinations were completed only 13 had developed influenza.
In the Worcester State Hospital vaccination was carried out after the epidemic had entirely subsided.
At the Bridgewater State Hospital no vaccines were used, but the morbidity rate was 29.9 per cent., as contrasted with 32.9 per cent. among the unvaccinated at Monson.
At the Danvers State Hospital the population of 853 adults was divided into three sections. One section was vaccinated with the Leary vaccine, one section with an unheated influenza vaccine prepared by Dr. Rosenau at the Chelsea Naval Hospital, and one section held as controls. The epidemic had, however, reached its height before vaccination was begun, and no information as to the relative value of the vaccines could be determined.
In Hinton’s (11) report the analysis covered the studies on about 6,000 vaccinated individuals, which represented slightly less than half of the population of 12 Massachusetts State institutions. Hinton’s conclusions were as follows: “The heated suspension of influenza bacilli used as a prophylactic vaccine did not prevent influenza, lessen its severity nor its complications, and, as far as could be ascertained, resulted in no harm.”
About the same time that Leary was working on his vaccine, Rosenau prepared an unheated suspension of Pfeiffer bacilli, isolated from cases of influenza of the existing epidemic, which he used at the Chelsea Naval Hospital and in an experiment at the Pelham Bay Naval Training Station. The writer is indebted to Surgeon-General of the Navy W. C. Braisted for the data from which this report was compiled—the report of the Sanitary Officer of the station not having been completed at the time the information was furnished. The vaccine experiment was made in the isolation regiment, which had remained practically free of influenza. Inoculations were begun on September 30, when 638 men were given the first dose of vaccine, 833 men being held as controls. On October 4 the second dose was given to 589 men,and vaccination was completed on October 8, when 565 men were inoculated. This group comprised the total number who received three inoculations. On October 14 practically all of these men were transferred, so that it was very difficult to get a complete record. Those cases which developed influenza prior to October 10 have been omitted by the writer, both from the control and vaccinated groups, because it is unfair to consider the incidence of influenza among controls which developed prior to the time the inoculations were completed in the vaccinated group. Between October 10 and October 24 there were 27 cases of influenza which developed among the vaccinated, and 30 among the controls, giving a morbidity rate of 3.6 per cent. among the 833 controls, as compared to 4.7 per cent. among the 565 vaccinated men. Emphasis is laid on the fact that these morbidity rates were calculated for both groups on the number of cases that appeared after vaccination had been completed. The result failed to show protective qualities in the vaccine.
Influenza vaccines for prophylaxis were also prepared in great quantities by the New York City Board of Health, and were made under the direction of W. H. Parke. No reports on the value of their vaccines have as yet appeared, and the writer has been unsuccessful in obtaining any data on the matter. The Parke vaccine was made in the following way: A large number of strains of Pfeiffer bacilli were isolated from cases of influenza during the epidemic. These were grown on a veal infusion agar containing 1 per cent. peptone, 0.5 per cent. of sodium chloride, 5 per cent. chemically pure glycerin, and the reaction of which was made neutral to phenolthalein in the cold. The agar was melted, and from 3 per cent. to 5 per cent. of citrated horse blood was added to it at a temperature above 95° C. The media was then slanted and cooled in 6 × 1 inch test tubes. Most of the vaccines contained about 17 different strains of Pfeiffer bacilli. The strains were inoculated separately on a series of slants, and at the end of 24 hours the cultures were washed off with sterile water and the washings from each series were placed in a separate bottle. Smears were then made to determine whether or not gram positive organisms were present, and as soon as each bottle was found to be free from contamination the contents were pipetted off into a 1,000 c.c. flask, and the dilution with sterile salt solution containing 0.25 per cent. phenol made. Allof the strains were mixed together in the large flask. A sample was then removed for standardization by Wright’s method, and the flask was submerged for one hour in water at 53° C. Transplants for sterility were made and watched for 48 hours. The vaccine was then diluted so that each cubic centimeter contained 1,000,000,000 Pfeiffer bacilli. Prophylactic vaccination was carried out by giving ½ c.c., 1 c.c. and 1½ c.c. doses at seven-day intervals.
At the request of the Department of Public Health of the city of Pittsburgh, the writer undertook to prepare Parke’s vaccine in large quantities. The vaccine was to be prepared under the direction of a committee consisting of Drs. Oskar Klotz, W. L. Holman, E. W. Willetts, George L. Hoffman and the writer, and the vaccine was to be turned over to the City Health authorities for distribution in the community. The work was carried out at the Singer Memorial Laboratory, and was begun the same day that the committee was appointed. Thirteen strains of Pfeiffer bacilli were used. Holman contributed six strains, isolated at autopsies done by Klotz at the Magee Hospital. Other fresh cultures were furnished by Willetts; Wiese, of the City Laboratory, and by the Singer Laboratory. The media used was that recommended by the New York Board of Health, save that sheep’s blood was used instead of horse blood because of convenience. The same technique was employed, with the exception that a modification of the Hopkins method of standardization was used instead of the Wright method. This was done because Pfeiffer bacilli are extremely small, tend to form unbreakable clumps and tangles, and so increase the difficulties of making satisfactory counts, either by means of the Wright method or with the Helber-Glynn counting chamber, that the methods are independable. Opalescent standards permit of such enormous variations that it was decided to use the Hopkins method, or a slight modification which we found so satisfactory that we will give our method here in detail.
When the sample was removed for standardization it contained not only a thick suspension of Pfeiffer bacilli, but also bits ofagar and blood-stained debris. It was necessary to rid the suspension of the gross contamination, and this was done at first by filtering it through sterile glass wool filters, and later by centrifuging it at slow speed for about 10 minutes. The suspension then contained little but the Pfeiffer bacilli, and was placed in the Hopkins tube and centrifuged for ½ hour on the sixth contact of the rheostat. This gave the per cent. of Pfeiffer bacilli in the suspension, and the necessary dilutions to make 1,000,000,000 per cubic centimeter were readily determined. The Hopkins tube consists of a centrifuge tube, with a capillary tube sealed on at the smaller end. The centrifuge tube is graduated in 10 c.c., 5 c.c. and 1 c.c. amounts, and the capillary portion is graduated in 0.01, 0.02, 0.03, 0.04 and 0.05 c.c. amounts. To standardize the vaccine, 10 c.c. of the sample was centrifuged in the tube and the amount of sediment read on the capillary scale. If the amount of bacilli fell between the graduations, an additional amount of sample was added, so that the sediment reached one of the graduated lines, the exact amount of sample added being noted. The percentage of the suspension could thus be determined by dividing the number of c.c. of sample used into the amount of the sediment obtained, and the number of bacteria calculated according to Hopkins table. The table available to us did not list the Pfeiffer bacillus, but according to it a 1 per cent. suspension of staphylococcus contains 10 billion organisms to the cubic centimeter, and we estimated that Pfeiffer bacilli were about half the size of staphylococci. This assumption was borne out by a number of Wright’s method counts on standardized suspension of bacilli. We, therefore, calculated that a 1 per cent. suspension of Pfeiffer bacilli should contain about 20 million organisms. Then, if 10 c.c. contain 0.02 c.c. of bacterial sediment, the per cent. was calculated by taking0.0210= 0.2 per cent., the strength of the suspension. If 1 per cent. contains 20 billion, then 0.2 per cent. contains 4 billion per c.c. In order to get a 100 million per c.c. suspension, it would be necessary to dilute the original suspension 40 times.
Every method of standardization is more or less inaccurate, but the above described method gave a fairly uniform product. Drying and weighing is claimed by many to be more accurate, but even with this procedure a fair amount of non-bacterial sediment is present in the material to be weighed.
After the vaccine was completed, cultures were made from the final dilutions and were watched for 48 hours. Mice and guinea pigs were injected with the first samples to make certain that the material was non-toxic. Two laboratory employees also volunteered and received full doses before the first batch of vaccine was released. The first five litres were turned over to the Red Cross on October 31, one week from the day the work was begun. In three more days the laboratory reached a capacity of 10 litres a day, and on the fifth day the order was received to discontinue preparation of the vaccine.
Relatively little of our vaccine was given out, and in the rush it was not possible to determine which physicians had been given our vaccine and which had received commercial mixed products, so there is no data on its protective powers.
As soon as we found that there was no call for prophylactic vaccines, we planned some animal experiments; but inasmuch as we were unable to get our cultures of Pfeiffer bacilli virulent enough to kill mice or guinea pigs, the minimum lethal dose could not be determined, and without it it was impossible to determine the protective value of the vaccine. Mr. Purwin, in our laboratory, injected a 25–gram mouse intravenously with 2 c.c. of a milk thick suspension of Pfeiffer bacilli without killing the animal. He was successful in getting a small needle into the tail vein and in slowly injecting the whole amount. The mouse was sick for about 36 hours, but entirely recovered. Guinea pigs were insusceptible to very large doses. Had we succeeded by means of a vaccine in completely immunizing a man against Pfeiffer bacilli, we still would have been uncertain that he was immune to influenza in its “epidemic” form.
The absence of virulence in our laboratory strains may not mean that the cultures were non-virulent when first isolated, but it suggests the uselessness of attempting to make active vaccines from strains kept on artificial media for months or years, such as those commonly offered for sale by commercial houses.
The loss of virulence in strains that have been isolated for some time is interesting in the light of Parker’s (12) work upon toxine production by Pfeiffer bacilli. She found that toxic filtrates appeared in infusion broth cultures in from 6 to 8 hours, and that 2 c.c. of a 20–hour filtrate would kill a medium-sized rabbit in from 1 to 3 hours. It was also found that the poisondeteriorated so rapidly that, in order to determine its toxicity, the tests had to be made on the same day that the filtrate was obtained. Parker succeeded in making an anti-serum against the poison, which appeared to be antitoxic for it both in vitro and in vivo. This work is interesting, and may be a step toward the development of a practical prophylactic serum.
From the above data, it is apparent that there is very little to indicate that an immunity to epidemic influenza is conferred by the use of a prophylactic vaccine composed of inert Pfeiffer bacilli alone. If a desirable vaccine is to be obtained through the use of these organisms, there must be radical changes in the mode of preparation of the vaccine or in the size of the doses given.
For some years commercial houses have been carrying mixed vaccines for the treatment of colds, which they called influenza vaccines. These preparations were made up usually of six or more different varieties of bacteria, and all of them were of similar composition. There was more or less variation in the doses, both as far as the total number of bacteria and the relative number of the different types were concerned. A typical example of a so-called “mixed influenza vaccine” may be given about as follows:
These vaccines were recommended in the various catalogues for use either alone or together with other vaccines in the prophylaxis and treatment of common colds, and in acute and chronic diseases of the respiratory tract. As a matter of fact, they hadbeen used very little in prophylaxis, and had failed to show very much value in treatment. In discussing these vaccines from the standpoint of treatment, R. M. Pearce (13) had the following to say: “A mixed vaccine for common ‘colds’ containing several organisms (staphylococcus, streptococcus, pneumococcus, micrococcus catarrhalis group, bacillus of Friedlander group, diphtheroid group, bacillus influenza) is one of the most recent bacterial ‘shotgun’ mixtures, which takes the chance of one lucky bull’s-eye in seven shots.” “No one can claim a scientific or even a common-sense basis for the treatment of a cold by such a mixture.” Catarrhal mixed vaccines of a similar kind were refused acceptance by the committee on “New and Non-efficial Remedies” of the American Medical Association, in June, 1918 (14), on the grounds that insufficient evidence of their therapeutic value had been furnished by their manufacturers.
While the above illustrates the status of “mixed vaccine” for therapeutic purposes, it is a well-recognized fact that it is possible to produce an immunity for most of the bacteria composing such vaccines, if killed cultures of the various strains are injected in sufficiently large doses. Again referring to Pearce’s article, we find the statement: “Prophylactic vaccination rests on a sound, scientific basis of experimental studies and clinical observation.”
The attempt to protect against epidemic influenza by the use of mixed vaccines was based largely on the following points. The medical profession was confronted by a rapidly approaching deadly epidemic, against which ordinary measures of control had failed. The epidemic was supposed to be due to a primary infection with Pfeiffer’s bacillus, but all of the fatal cases were found to have profound secondary or symbiotic infections, with one or more of the strains contained in the “mixed vaccines.” It was known that mixed bacterial proteins, even though they were not actually specific, possessed certain qualities of producing reactions unfavorable to infections in general, which were characterized by a temporary rise in temperature, by an increase in the number of leucocytes, and by a more or less demonstrable amount of active immunity against each one of the contained bacterial toxins. The artificial production of a leucocytosis was especially desirable, because a characteristic of epidemic influenza was the failure of leucocytosis on the part of the infected individual. In other words, mixed vaccines were used because they were theonly available substances which offered the hope of creating a reaction against the secondary invaders which were so commonly the cause of death in influenza.
Since Pittsburgh’s experience with prophylactic vaccination had chiefly to do with the use of commercially prepared mixed vaccines, a brief history of the local experience with them may be of interest.
About the time that the first cases of influenza were being reported from the Pittsburgh district, articles on preventive vaccines as used in Boston and at some of the camps began to appear in the daily papers, shortly after which came the announcement that the Carnegie Steel Company was offering free vaccination to their employees and to the families of their employees. Dr. W. O. Sherman, chief surgeon for the company, advocated the use of the vaccine because he hoped to increase the immunity to secondary infection and to produce an active leucocytosis in the vaccinated individuals, and at the same time to allay panic among the employees at a time when an interruption of manufacturing and mining pursuits might be disastrous to the entire country; and he did it with the assurance that if the vaccine did no good, it would at least do no harm. He took steps to arrange for the collection of data by which he hoped to determine whether or not the vaccine as used by their company did any good. His report has not yet appeared. Other large corporations at once instituted prophylactic vaccinations with commercial “mixed vaccines.”
In contrast to the altogether laudable efforts of these companies to protect their employees, a complete history of the vaccine episode in this community necessitates the recounting of a very different phase in the matter. When it became known that corporations were vaccinating their employees, people in general naturally began to investigate. Physicians’ offices were besieged by persons who either demanded vaccination at once or wanted to know whether or not there was “anything in it.” Conscientious physicians in their turn called up the offices of the medical societies, the various laboratories, and telegraphed everywhere trying to get some definite data before recommending the vaccine to their patients. It was impossible to answer the question definitely, because it was a new procedure and purely in the experimental stage. On the whole, the medical professionhandled the situation in a competent and dignified manner, for the great majority gave vaccines only after a full explanation to the effect that its value was in doubt, or else refused to give it altogether. There were some, however, who were not conscientious, and the unscrupulous practitioner seldom had a better chance to impose upon the public. The demand for vaccine soon exceeded the supply, and it is claimed that there were doctors who gave any type of vaccine they could obtain without regard to its bacterial make-up or intended purpose. Anti-diphtheritic serum was given in many instances, and it is said that even normal salt was used. Statements to the effect that exorbitant sums were being charged and that guarantees of prevention were being made resulted in the Red Cross Society undertaking the distribution of the vaccine. To protect itself, the Medical Society issued the following notice in the weekly bulletin for October 26, 1918:
The Society wishes it understood that at present there is no vaccine, serum or inoculation which will secure anyone against influenza. It is desirable that everyone should avoid hysteria and consider only the reports which are officially given out by the Health Department, since of late various methods of prophylaxis and treatment have found their way into the daily newspapers, and these may prove harmful rather than do good.
Almost simultaneously the daily papers published the report of Surgeon-General Blue, of the United States Bureau of Public Health, which expressed practically the same opinion. It was not the intention of either of these articles to criticise the practice of vaccination, but merely to warn the public against profiteering and fraudulent guarantees. They had the unexpected effect, however, of causing people to completely lose faith in prophylactic vaccines, and in many instances to become actually antagonistic to them. It was during this period that the preparation of vaccines from pure influenza strains was undertaken, under supervision of the County Society and for distribution through the Department of Public Health. Two days after the first supply of this vaccine was ready the Red Cross authorities telephoned that there was no further call for vaccine. The man in charge of the distribution stated concretely that “the bottom had dropped out of the vaccine business.” A few days later theDepartment of Health issued an order to stop the preparation of the vaccine.
Many pharmacies, having small supplies of vaccines, realized the great call for it and the difficulty of obtaining a new supply, and were also guilty of commercialism. Certain of the large biological product companies were no exception. One house issued a hand-bill, printed in red on a yellow background, which stated: “Epidemic influenza is due to the influenza bacillus. The present epidemic of influenza has a tendency to develop pneumonia. The use of our influenza bacillus vaccine No. —— will abort the influenza and avoid pneumonia and other sequelæ. When pneumonia has developed, it can be reduced to less than one-third the mortality and duration usual with other methods of treatment,” etc. Practically all of the above statements are still unproven, and probably will never be shown to be true. Such a bulletin undoubtedly lays this firm of vaccine manufacturers open to prosecution under the law protecting against false and fraudulent advertising. Several fairly well-authenticated incidents occurred in which the representatives of vaccine houses offered factory managers and others share and share alike in the profits, if the brand of vaccine made by them was used. It is on such happenings as the above that the writer advocates legal measures, allowing Boards of Health to control the advertising of remedies and distribution of biological products during epidemics.
How much Pittsburgh will learn from the experience with vaccines will depend on the numerous analyses of data which were acquired during the epidemic.
Proof of the prophylactic value of mixed vaccines for epidemic influenza depends entirely upon the results of its practical application to human subjects in times when the disease is prevalent. Animal determinations are out of the question, because it has not been possible to produce the epidemic form of influenza experimentally. If all people were equally susceptible and were equally exposed, it would be a simple matter to compare the number of vaccinated persons who developed the disease with the number of unvaccinated persons who contracted it; but since many thousands were vaccinated and some of them contractedthe disease in spite of it, and a greater number of persons who were not vaccinated entirely escaped, the analysis is extremely difficult.
The time element is a big factor. In instances where vaccination was completed in a community before the epidemic appeared there, the figures are worth more than those in which vaccination was undertaken after the epidemic had become established. This is true, because the most susceptible persons in a community developed the disease as soon as they were exposed, the less susceptible ones were not attacked until later, and the insusceptible ones escaped altogether. Whenever vaccination is begun during an epidemic, the persons vaccinated for prophylactic purposes are necessarily chosen from those who have not yet developed an attack. The later in the epidemic that vaccination is begun, the greater will be the number of persons selected for vaccination from among those more or less naturally immune. Then, if the total number of cases among the vaccinated is compared with the total number of cases among the unvaccinated, the apparent value of the vaccine is increased; but the estimation is not a fair one, because the vaccinated group is unavoidably selected from among relatively immune persons, while the controls include all of the very susceptible people who were suffering from the disease at the time vaccination was begun. Where vaccination is begun after the epidemic is advanced, the only figures worth while are those obtained by a day-by-day or a week-by-week comparison between the number of cases developing among controls and the number of cases appearing among those vaccinated, and by beginning that comparison at a time subsequent to the day on which the prophylactic inoculations were completed.
Aside from the interpretation of the results there is possibly a more serious reason for objecting to the beginning of vaccination during an epidemic. This lies in the danger of producing a temporary negative phase in the patient, which makes him somewhat more susceptible to natural infection for a few hours immediately following each administration.
McCoy (15) outlined the requirements necessary for an ideal vaccine experiment as follows: 1. The community should be as large as possible, and should number at least 10,000 persons. 2. The conditions under which they live should be as nearly equal as possible. 3. The turnover, or rather the change in population,should be as small as possible. 4. The social service should be efficient and reliable, so that it can be definitely ascertained when anyone becomes sick and what the disease is from which he is suffering. 5. Fifty per cent. should be vaccinated before the epidemic arrives, and the other 50 per cent. should be held as controls.
No examples were found which came up to the above requirements, but there were some instances in which vaccination was completed before the epidemic appeared, and some in which we were able to get a week-by-week comparison between vaccinated and unvaccinated groups. Most of the data which has been reported shows that vaccination was begun about the last of the second or the first of the third week of the epidemic, and in some instances not until after the peak was passed. Add to this the fact that the vaccine was given in from three to four doses, at from three to seven day intervals—a course which required in the neighborhood of two weeks for completion—and it is obvious that the full protective powers of the vaccine were not acquired by the individual until the worst of the epidemic was over and the number of cases were rapidly subsiding.
In order to get the best understanding from these experiments, the data will be presented in three series: I. Those instances in which vaccination was completed before the epidemic appeared. II. Those instances in which it is possible to compare the relative occurrence of influenza in both the vaccinated and unvaccinated groups after vaccination was completed. III. Those instances in which vaccination was begun after the epidemic appeared and in which comparisons of total figures only are available.
1. The only instance in the Pittsburgh community in which vaccination was completed before the epidemic appeared is that reported from the Dixmont Hospital, Dixmont, Pa., and furnished me through the courtesy of Dr. Hutchinson (16). The institution had a population of about 1,000 patients and 300 employees. Prophylactic vaccination was begun on October 20, and was completed about November 6. Each c.c. of the vaccine used contained 200,000,000 each of B. Pfeiffer, Micrococcus Catarrhalis, B. Friedlander,Pneumococci, Streptococci and Staphylococci, both Aureus and Albus. Four doses were given of 4 minims, 8 minims, 12 minims and 16 minims, respectively. Inoculations were carried out at four-day intervals. Owing to the isolation of the institution from the general community, the first case did not appear until two weeks later—namely, on November 20. The results are shown by the table.
None of the vaccinated patients developed pneumonia, though there were 15 cases among the unvaccinated.
This experiment shows a slight percentage in favor of vaccination, and indicates that there was some decrease in the severity of the secondary infections.
2. The experiment reported by McCoy, Murray and Teeter (17) showed quite opposite results from the above, and was an excellent example of a small though completely controlled test. In an asylum for the insane in San Francisco all of the patients under 41 years of age were divided into two groups—one group was kept as controls and the other was given a vaccine furnished by F. O. Tonney, of the Chicago Health Department. The vaccine contained 500,000,000 each of B. Influenza, Pneumococcus I, II and III, 1,500,000,000 Pneumococcus IV, 1,000,000,000 Streptococcus Hæmolyticus and 500,000,000 Staphylococci. Doses of 0.5 c.c., 1 c.c. and 1½ c.c., which were given at 48–hour intervals. Inoculation was completed on November 15, and the first case of influenza appeared on November 26. The table shows the result.
3. The report of Minaker and Irvine (18) included several groups of men, the first two of which apparently belonged in our first series. They used a vaccine, each c.c. of which contained 5,000,000,000 B. Pfeiffer, 3,000,000,000 each of Pneumococcus Iand II, 1,000,000,000 Pneumococcus III, 100,000,000 Streptococcus Hæmolyticus. In all, they vaccinated 11,179 persons.
(a) Their first group numbered 4,950 persons in quarantine at the Naval Training Station. The quarantine was maintained for 24 days, and no influenza appeared during that time. Three thousand five hundred and fourteen of them were released at a time when there were still 200 to 300 cases of influenza being reported daily in San Francisco. Out of the 3,514 men, 15 had influenza, and there were no deaths.
(b) At the Mare Island Navy Yards 1,950 marines were released immediately after completion of the inoculation. They were turned into Valejo and San Francisco, where influenza was at its height. Only 35 cases, with 1 death, occurred, and these developed shortly after the men were released in San Francisco. This group was controlled with an unvaccinated group of 8,232 persons who remained at Mare Island, and 1,296 cases of influenza, with 65 deaths, occurred among the controls.
(c) At San Pedro 3,100 were vaccinated, and of these 53 had influenza, and there were no deaths. The occurrence among these was compared with the prevalence of the disease in Los Angeles, but this part of the report leaves much to be desired in the way of the relative dates, etc.
(d) The fourth group, consisting of 1,080 civilians, developed 14 cases, with no deaths. However, vaccination of this group was not completed until 21 days after the pandemic had appeared in the community. Minaker’s and Irvine’s analyses show a favorable percentage for vaccination in the first two groups, but their groups three and four were not sufficiently well controlled to be of much help.
4. In a report which appeared during October, 1918, Eyer and Lowe (29) published the results of prophylactic inoculation of 1,000 New Zealand troops with a mixed catarrhal vaccine. They controlled their experiments with 19,000 New Zealand troops who were not inoculated. A comparison of the incidence of acute respiratory disease and influenza during the primary wave of the epidemic as it appeared during June and July, gave two cases among the vaccinated troops and an average of 43.2 cases per thousand among the controls.
Later they reported (58) the results of much larger experiments as carried out at 17 different camps and hospitals. The vaccine which they used was a typical “mixed” vaccine, save thatthe authors emphasized the advantage of using strains not more than three generations removed from the body. At some of the camps their reports were unfavorable, but upon the whole their results, as summarized below, were most encouraging. In most instances inoculations were completed just prior to the arrival of the autumn epidemic.
Out of a total average strength of 21,759, approximately 16,104 men received full prophylactic vaccination, and approximately 5,700 were uninoculated, or had received only 1 dose; 3,366 cases of influenza developed—15 per cent.; 1.3 per cent. occurred among the vaccinated, while 4.1 per cent. developed in the uninoculated; 8 per cent. of the severe cases among the protected died, as compared to 23 per cent. among the uninoculated. The death rate for all infected cases was 0.26 per cent. among the inoculated and 2.2 per cent. among the uninoculated.
Notanda.—All of the above reports, comprising the “Series I” experiments, indicate that mixed vaccines reduced the number of severe illnesses and lowered the death rate to some extent.
1. The report on prophylactic vaccination at the Hospital for the Insane at Retreat, Pa., was very kindly furnished by Dr. Charles B. Maberry (20). When the epidemic approached, the institution was placed in quarantine and remained free from influenza until October 28, when two cases appeared in nurses who had broken quarantine. Influenza spread in the male ward, but the female wards were kept free during the whole of the epidemic. There were 370 male patients, but 60 were in the infirmary and were not included in the calculation. Out of 310 patients, 210 received vaccines. Ordinary commercial mixed vaccine was used, and vaccination was begun two days after influenza appeared. During the first week there were 40 cases of influenza, 6 of which occurred among those who had received a single dose of the vaccine. After the first week there were 38 cases of influenza, with 10 pneumonias and 5 deaths, among the unvaccinated, giving a morbidity rate of 38 per cent. and amortality rate of 5 per cent. In the vaccinated group there were no cases after vaccination was completed. Maberry states further that in ward III the only cases which appeared subsequent to vaccination were in six patients who refused preventive inoculations. This appears to be the most favorable of any of the reports.
2. Nurses on duty in hospitals everywhere suffered greatly from influenza, and those of Pittsburgh were no exception. Some of the hospitals vaccinated the nurses during the epidemic and some did not, and it was hoped that by getting a week-by-week comparison of the number of cases among vaccinated and non-vaccinated nurses some reliable data would be obtained. A circular letter sent to all of the hospitals in the community contained a blank asking for the number of nurses, date of appearance of the epidemic, use of vaccine, dates of inoculations, and for a week-by-week occurrence of influenza in each group. Only 7 hospitals complied with the request, and of them only 5 sent complete data. Complete reports were received from the Allegheny General, Columbia, Presbyterian, South Side and St. Francis Hospitals. Of a total of 336 nurses in these 5 institutions, 38 developed influenza in the first week, 48 in the second, 39 in the third, 43 in the fourth, and 45 subsequent to the fourth week, making a total of 213—a morbidity of 63 per cent. The Mercy and St. Margaret’s Hospitals reported the total number of nurses and the occurrence of influenza among them, and adding in their reports there were 521 nurses on duty in 7 hospitals, with 257 cases of influenza, giving a morbidity rate of 50 per cent.; 28 cases of pneumonia and 11 deaths, giving a 2 per cent. mortality rate. The total figures from hospitals where vaccines were used are against vaccination, due partly to the fact that vaccination was started late. In these hospitals the morbidity was 66 per cent. and the death rate 3 per cent. In the hospitals where vaccines were not used the morbidity rate was 20 per cent. and the death rate 1.2 per cent. No dependable data was obtained, but the report from the South Side Hospital was interesting. Of 60 nurses on duty, 36 had influenza and 2 died. Of this number 19 were stricken the first week. Three days after the first cases were admitted to the hospital vaccination was begun, and was given to most of the nurses still on duty. Of those taking vaccines 20 developed influenza and 1 died during the period ofimmunization, but after the inoculations were completed there were no more cases in either group.
During the epidemic it was said that benefit was derived from the use of vaccines on nurses at the West Penn Hospital, but the writer was unable to obtain a report from this institution. The collected data on nurses was useless, though it is interesting, in that it shows the possibility of making figures prove almost anything you want them to prove.
Undoubtedly the largest attempt at prophylaxis against epidemic influenza through the use of “mixed vaccines” was that made under the direction of Dr. W. O. Sherman for the Carnegie Steel and H. C. Frick Coke Companies. The results which Dr. Sherman hoped to attain when he planned using the vaccine and collecting the data have already been given. Commercial mixed vaccines similar to those described under the “Series I” experiment were used, and four doses, three days apart, were given. Inoculations were begun on October 20, 1918, and were completed during the first week of November. Vaccine was administered to the employees and their families without charge. Later cards were given to all employees, and they were made to fill them out and return them. On the cards were blanks calling for the name, age, sex, color, number of inoculations, whether or not the employee himself or any member of his family had had influenza, and how many days the sick individuals had been in bed. Each mill and mine was then supplied with a set of blank forms providing for a complete statistical record of the number of inoculations and the total incidence of influenza, pneumonia and death. From the reports of the respective mills and mines the total figures given in the charts were compiled.
Difficulties were encountered in every part of the work. The vaccine demand was so great that the products of three different firms were used. So many doctors were in service that most of the vaccine had to be given by carefully coached nurses. The bulletins of the United States Bureau of Public Health and of the Allegheny County Medical Society, with their warnings about influenza vaccines being only in the experimental stage, appearedjust at the time the work was begun and caused a great many to refuse to complete vaccination after one or two doses had been given. So few medical men were left that it was impossible to have them see all cases and so determine the nature of many of the illnesses which were occurring. It was assumed, therefore, that any employee who had fever and was sick for a period of three days had influenza, and that any who were confined to bed for seven days or more had pneumonia. The figures of the central offices were made up from the reports of 14 steel mills, 1 cement factory, 4 warehouses and 57 mining districts. The accuracy of data depended on the careful work of a great many local statistical workers, which made individual variations hard to control. The greatest difficulty of all, however, lay in finding a common basis for comparisons of the incidence of influenza, pneumonia and death in the vaccinated and non-vaccinated groups, since the data on the former group included the occurrence only after the peak of the epidemic had been passed, and that of the latter group included the occurrence for the entire epidemic.
The total figures are given in the three charts.