Age-related response to 1000 CCA unit zonally purified, inactivated influenza vaccines in volunteers in the U.S.A.

Response to 1000 CCA unit Aichi/68 and Japan/57 influenza vaccines was studied in 687 volunteers from ages 6-101 in the summer of 1971. The vaccines, prepared by zonal ultracentrifugation, were well tolerated in all age-groups. Antibody responses were comparable with each vaccine and were strongly influenced by age of the volunteer. Persons born since 1940 (age 31 and under) had a much more impressive response as determined by both overall geometric mean titre rise and% with ≥ four-fold increase in titre than persons born before 1940. The most reasonable explanation for this phenomenon seems to be the greater prior exposure of the younger age-groups to the strains in the vaccines. It is concluded that more attention needs to be given in the future to assessing vaccine potency in the age-groups for which the maximum protection is desired, namely, the elderly.