Clinical reactions and serologic responses after vaccination with whole-virus or split-virus influenza vaccines in children aged 6 to 36 months.

The reactogenicity and immunogenicity of whole-virus and split-product influenza vaccines were studied in 77 children between the ages of 6 and 36 months. Subjects initially received monovalent vaccine containing either A/USSR/77 (H1N1) antigen in 1978 or A/Brazil/78 (H1N1) antigen in 1979. One month later a trivalent preparation was given which contained the respective H1N1 antigen plus A/Texas/77 (H3N2) and B/Hong Kong/72 antigens. Temperatures of greater than or equal to 37.8 C (greater than or equal to 100 F) were observed more commonly after initial vaccination with whole-virus vaccine (35%) than after split-product vaccine (14%). No child had a temperature of greater than or equal to 39.4 C (103 F) or a febrile convulsion. The trivalent vaccines were more reactogenic than the monovalent vaccines although none of the reaction indices exceeded 0.9. The whole-virus vaccine appeared to be more immunogenic, especially in those children who were initially seronegative (preimmunization hemagglutination-inhibiting antibody titer (less than 5). Only 50% of children vaccinated with split-product vaccines with initial hemagglutination-inhibiting titers of less than 5 achieved titers of greater than or equal to 20 to the H1N1 antigen after two doses of vaccine compared with 97% in similar whole-virus vaccine recipients. The degree of antibody response to the A/Texas/77 component of the vaccines was greater than the response to the A/Brazil/78 or A/USSR/77 antigens.

Influenza immunization in children and young adults: clinical reactions and total and IgM antibody responses after immunization with whole-virus or split-product influenza vaccines.

Clinical reactions and hemagglutinating-inhibiting (HAI) antibody responses to recent whole-virus and split-product influenza vaccines were studied in 168 children and young adults. The subjects initially received a monovalent vaccine, followed one month later by a trivalent preparation. The reactogenicity of whole-virus and split-product vaccines with an equivalent hemagglutinin content was similar except in the youngest age (6 to 36 months) group in which the whole-virus preparation was more reactogenic. The whole-virus vaccines were more immunogenic, especially in subjects who were previously unprimed (preimmunization HAI antibody titer, less than 5). In these subjects, the geometric mean titers of HAI antibody wee significantly higher after vaccination with whole-virus vaccines than the split-product vaccines. Specific IgM antibody was found more frequently after vaccination with whole-virus vaccines (34%) than after split-product vaccines (11%).