Comparison of heterotypic protection against influenza A/Taiwan/86 (H1N1) by attenuated and inactivated vaccines to A/Chile/83-like viruses.
 Children (n = 192) aged 3-19 years from 98 families completed this double-blind, placebo-controlled study comparing the efficacy of a bivalent attenuated (CR) vaccine with trivalent inactivated (TI) vaccine.
 Both vaccines contained A/Chile/83 (H1N1)-like antigens.
 After vaccination the geometric mean titer to A/Taiwan/86 (H1N1) was 1:36 in the CR group, 1:92 in the TI group, and 1:5 in the placebo group.
 During the influenza A/Taiwan/86 (H1N1) epidemic, 21.4% of CR recipients, 16.7% of TI recipients, and 43.9% of placebo recipients were infected with influenza A/Taiwan.
 TI vaccine provided better heterotypic protection than did CR vaccine for children aged 10-18 years (infection rate, 0 vs.
 24%, respectively; P less than .025); in contrast, in the younger children (3-9 years), CR vaccine tended to be more protective (19% vs.
 26% for TI).
