a total of 1,995 primary school children ( 1,464 vaccinees and 531 non-vaccinees ) were studied to evaluate the protective efficacy of tween-ether split trivalent a ( h1n1 ) , a ( h3n2 ) , and b influenza vaccines by comparison of the incidence of confirmed infection in two groups during 1980 to 1984 .
C0021403
influenza vaccines
C0009450
infection