Safety and antigenicity of influenza A/Hong Kong/68-ts-1 (E) (H3N2).

Influenza A/Hong Kong/68-ts-1 [E] (H3N2) vaccine was administered intranasally to 18 seronegative children 14 to 32 months of age. Fourteen children, 78%, shed influenza A/Hong Kong virus for a mean of eight days following vaccination. Sixteen children, 89%, experienced a fourfold or greater rise in hemagglutination-inhibition antibody. Some children appeared to experience a febrile reaction to the vaccine although interpretation of this data was complicated by intercurrent illness. These findings demonstrate that influenza A ts-1 [E] replicates more readily in the young seronegative child than in the HAI negative adult. In addition, the temperature-sensitive marker of the vaccine was not genetically stable in four of the vaccinated children. Careful evaluation of any future live respiratory viral vaccines needs to be undertaken in the young seronegative child before the vaccine's safety is fully established.