Evaluation of a temperature-sensitive influenza virus in elderly and chronically ill subjects

A temperature-sensitive influenza virus, influenza A/Hong Kong/68-ts-1 (E), was administered to 18 elderly subjects and to 18 chronically ill subjects. Clinical reactions were infrequent (n = 3), mild, and afebrile. Vaccine virus was recovered from 5 subjects. Serum-neutralizing antibody responses to A/Hong Kong/68 antigen were detected in 13. Serum hemagglutination inhibiting antibodies were detected in 6 to A/Hong Kong/68 antigen and in 7 to A/England/42/72 antigen. Nasal antibodies were detected in 3. Using any criteria, a total of 17 patients developed evidence of infection, and occurrence of infection was related to concentration of serum antibody before inoculation. Transmission of vaccine virus may have occurred to one of 10 uninoculated subjects. In the presence of a naturally occurring outbreak of influenza A/England/42/72, 15 ts-1 (E) vaccines and 17 of 42 persons who had received parenteral vaccine became ill. Evidence of infection with influenza virus was obtained in 8 of the former and 10 of the latter group.