Influenza a in a Vaccinated Population

Vaccination of man against epidemic influenza has given promising results in controlled studies during the past few years. Whereas earlier experiments yielded suggestive, equivocal or negative data, the development of vaccines prepared by various means from allantoic fluid infected with influenza virus led to the demonstration of definite protective effects by such preparations both under conditions of epidemic1and experimental exposure of vaccinated persons to influenza virus.2Thus the reports of the members of the Commission on Influenza of the Army Epidemiological Board indicated a reduction in the incidence of the disease of about 70 per cent in the influenza A epidemic of 19431and of 90 to 95 per cent in the influenza B outbreak of 1945.3 Encouraging as these results were, reservations had to be made because of proved antigenic differences between various strains of influenza viruses of either type. Such differences were readily