IMMUNIZATION AGAINST INFLUENZA WITH OBSERVATIONS DURING AN EPIDEMIC OF INFLUENZA A ONE YEAR AFTER VACCINATION12

Abstract

A study of the efficacy of vaccination against influenza was undertaken during the winter of 1942-1943 in 2 institutions in Michigan. Approx. 7,800 individuals were involved, half received a formalinized, concentrated prepn. of influenza virus vaccine, Types A and B, and the remainder received an inoculation of salt soln. The anticipated outbreak of influenza did not occur until the following winter of 1943-1944. At that time observations were made at one of the institutions. The indications that vaccination had a protective effect against influenza A have been presented and discussed. Antibody response to vaccination was detd. in about 10% of the vaccinated group and revealed that 2 weeks after vaccination the mean titer for Type A virus was raised about 9-fold and for Type B virus was raised about 8-fold. Anti-body titers in the majority of vaccinated individuals were raised to levels beyond the highest observed before vaccina-tion. The serol. data have been analyzed in a variety of ways and these have been discussed. The duration of the increased antibody titer for as long as 1 yr. after vaccination was detd. and revealed that the distribution of antibody titers was still considerably above that observed before vaccination. Data are presented which show that the vaccine used was stable for more than a yr., when stored in the refrigerator, as detd. by mouse-protection tests and capacity to induce a rise in anti-body in man.