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 poison deteriorated 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.

Conclusion

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.

The Attempt to Protect Against Epidemic Influenza by the Use of Mixed Vaccines

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:

B. Influenza (Pfeiffer)25to400million per c.c.
M. Catarrhalis25to400million per c.c.
B. Friedlander25to400million per c.c.
Pneumococci25to400million per c.c.
Streptococci25to400million per c.c.
Staph. Albus-Aureus50to800million per c.c.
Totals175to2800million per c.c.