Immunogenicity and Reactogenicity of 1 versus 2 Doses of Trivalent Inactivated Influenza Vaccine in Vaccine‐Naive 5–8‐Year‐Old Children

Abstract

BackgroundTwo doses of trivalent inactivated influenza vaccine (TIV) are recommended for children MethodsIn this prospective, open-label study, 232 influenza vaccine–naive 5–8-year-olds enrolled in a health maintenance organization received 2 doses of TIV in fall 2004. Serum for antibody titer measurement was obtained at 3 time points (n=222). Parents completed diaries for 5 days ResultsBoth doses of vaccine were well tolerated. The strongest predictor of a protective antibody response (⩾1:40) after 1 dose of TIV was baseline seropositive status. In multivariate analysis adjusting for age, sex, and baseline serostatus, the proportion of children with protective antibody responses was significantly higher after 2 doses than after 1 dose of TIV for each antigen (P<.001, for A/H1N1; P=.01, for A/H3N2; P<.001, for B). Age and sex were not independently predictive of a protective antibody response. Over one-third of children had antibody responses ConclusionsThe present study supports the need for 2 doses of TIV in 5–8-year-olds receiving TIV for the first time. Efforts to increase compliance with the 2-dose recommendation are warranted