Importance of Antigenic Composition of Influenza Virus Vaccine in Protecting against the Natural Disease

Abstract

1. In the winter of 1947-1948 studies on vaccination against influenza were carried out in a military installation. Due to limiting circumstances that are described, the study involved a comparison of two vaccines that differed in strain composition. Representative strains of Type A and Type B viruses were present in both. However, only one of the two vaccines contained, in addition, the antigenic variant of the Type A strain (referred to as A-prime) that was prevalent during the winter and spring of 1946-1947. 2. The entire population was vaccinated; men with odd aerial numbers received one of the vaccines and the even-numbered men received the other. Records were kept of admissions to hospitals and to quarters for all diseases. The data revealed that the group given the new-formula vaccine, which contained the A-prime antigen, experienced approximatel1. Salk JE, Suriano PC. Importance of antigenic composition of influenza virus vaccine in protecting against the natural disease. Am. J. Public Health 1949; 39:345–355. y 100 fewer cases of respiratory disease. As for other illnesses there was no difference, in this respect, between groups given the different vaccines. 3. Serological tests of acute and convalescent sera revealed the occurrence of a small proportion of cases of influenza virus infections during the period of increased prevalence of respiratory disease. Moreover, from the serological studies it appears that the prevalent virus was related to the A-prime sub-group, which was represented in only one of the two vaccines. 4. These observations indicate that during a period in which influenza occurred sporadically or endemicaUy, the use of a vaccine having the specific as well as the broader antigenic coverage, was effective in reducing the number of cases of respiratory disease. 5. The significance of the existence of antigenic varieties of influenza virus strains is discussed in relation to the problem of immunization.