Vaccination in 1918 was much different than we know it today. Vaccines were often prepared by individual physicians or small pharmacies, not large companies the way they are today. There were dozens of different preparations, many of them proprietary. Inductees into the U.S. Army typically received a battery of shots from bottles of vaccine that in many cases were months old and allowed to sit in warm storage rooms for weeks at a time. Preservatives of the time were much less effective than those used today, and in some cases vaccines were not preserved at all. The opportunity for contamination should be obvious, even to a lay person.

As an example of a typical vaccine from 1918, I have excerpted below a recipe published by E.C. Rosenow, a doctor from the Mayo Clinic in Rochester, Minnesota. Rosenow's vaccine was widely used during the hysteria of 1918. From the text below you can see how dangerous this preparation was. Any failure of sterilization can easily result in contamination. Rosenow recommends the use of cresol as a preservative. Cresol is the same thing as Lysol. Although better than nothing, modern biochemists would consider it inadequate and unsafe. Note that he mentions "reactions" in the text. At that time it was common for patients to have serious inflammatory reactions in response to vaccination. The reason for this is both the cresol and also the use of bacterial matter in the vaccines. Bacteria have a natural defensive toxin in their skin called endotoxin. This poisonous organic material is released when the bacteria is killed or dies naturally.

Of course, this "vaccine" against influenza was useless. As we know today, colds are caused by viruses and there is no such thing as an "influenza bacteria." In 1918, physicians mistakenly thought that colds were caused by bacteria. They also did not realize that a bacterial innoculation was useless. Bacteria like Pneumococcus are pervasive in the natural environment and everyone's body has antibodies against it since birth. There is no need and no purpose to "innoculate" a person against Pneumococcus or other common bacteria. In the paper cited below, not only did Rosenow fail to realize these basic things that we know today, but he also describes a study he conducted purporting to show the effectiveness of his vaccine. According to the study, his vaccine reduced the likelihood of an influenza infection by up to 75%. Of course, today we can recognize this study as biased and worthless, but at the time he was a highly regarded scientist and doctors implicitly trusted his research.

Verbatim extract from "Prophylactic Inoculation Against Respiratory Infections During the Present Pandemic of Influenza."
by E.C. Rosenow, Mayo Clinic, Rochester, Minnesota
Presented before the American Public Health Association, Chicago, Dec. 10, 1918.
First published in the Journal of the American Medical Association, 1919, lxxii, 31-34.

Preparation of the Vaccine

The formula of the vaccine used during the earlier part of the epidemic, and used exclusively in the cases in this report, is given in Table 1.

TABLE 1. FORMULA OF VACCINES

Pneumococci Types I (10 per cent), II (14 per cent), and III (6 per cent)	30 per cent
Pneumococci Group IV and the allied green-producing diplostreptococci described	30 per cent
Hemolytic streptococci	40 per cent
Staphylococcus aureus	10 per cent
Influenza bacillus	10 per cent

The bacteria were grown for from eighteen to thirty-six hours at from 33 to 35 C, in 0.2 per cent glucose broth. The broth was autoclaved at 20 pounds pressure for from one to two hours to insure freedom from living spores. The glucose was added in a sterile manner from a concentrated sterilized solution in water. It was found that the cultures of pneumococci and streptococci yielded approximately 1000 million bacteria and Staphylococcus aureus 2000 million bacteria per cubic centimeter. Luxuriant growth (about 1000 million per cubic centimeter) of the influenza bacillus was obtained by adding approximately 1 c.c. of laked human blood per liter of glucose broth. The strains were grown separately in the flasks. Smears were made before centrifugation of each flask to eliminate possible contaminations. The pneumococci and allied green-producing streptococci, the staphylococci, and influenza bacilli were separated from the broth culture by centrifugation, and then suspended in sodium chlorid solution. At first 50 per cent of the hemolytic streptococci were added in the form of the killed broth culture and the other 50 per cent in sodium chlorid solution suspension after centrifugation. But owing to rather severe reactions, only 25 per cent of the hemolytic streptococci are added in the form of the broth culture. The streptococci in the broth culture are killed by the addition of 0.5 per cent cresol. The centrifugated bacteria are suspended in sodium chlorid solution so that 1 c.c. represents approximately the growth from 50 c.c. of the broth culture, and are killed by the addition of 1 to 1.5 per cent purified cresol. The dense suspensions are diluted with an equal volume of sodium chlorid solution after the cultures, made twenty-four hours after the cresol is added, have remained sterile for forty-eight hours. In some instances the suspensions became slightly contaminated with Bacillus subtilis, when heating to 60 C. for one hour was necessary to render them completely sterile. If this was not sufficient, the suspensions were discarded. At first, owing to the urgent demand for the vaccine, the use of extreme heat in the sterilization of the broth, negative aerobic and anaerobic cultures at the end of from forty-eight to seventy-two hours were considered sufficient as sterility tests. It is now the rule to hold the vaccine until all cultures and animal tests have proved negative for one week. Blood-agar and glucose broth and glucose brain broth and litmus milk in tall columns are the mediums used for the sterility tests. It was the rule to inject a number of persons with each batch of vaccine before it was sent out for general use. The vaccine is finally made up by diluting the dense suspensions in the proper proportions with sodium chlorid solution so that 1 c.c. contains approximately five billion bacteria. Purified cresol (0.3 per cent) is used as a preservative. The initial dose for adults is 0.5 c.c. subcutaneously. This is followed in one week by 1 c.c. The third dose is given fourteen days after the first dose and consists of 1.5 c.c. The doses in children are 0.1, 0.2, and 0.3 c.c. or more according to age. Owing to the relatively large doses, intervals shorter than one week between injections are considered inadvisable.