Children aged 5–8 years who have not previously received a flu vaccine need two doses of trivalent inactivated influenza vaccine, based on antibody response data from 222 children in a prospective, open-label study.
Prior studies have established the need for two doses of flu vaccine for unvaccinated infants and young children, but research in older children has been limited, said Dr. Kathleen M. Neuzil of the University of Washington, Seattle, and her colleagues (J. Infect. Dis. 2006;194:1032–9). Dr. Neuzil has received grant support from Sanofi Pasteur and MedImmune.
Among children who were seronegative at baseline, an additional 50%, 51%, and 31% developed protective responses to A/H1N1, A/H3N2, and B vaccine antigens, respectively, after a second dose of trivalent inactivated influenza vaccine (TIV).
Baseline seropositive children showed a significant increase in antibody titers after one dose, but they showed no significant additional difference in antibody titers after a second dose (see box).
The results remained significant after controlling for baseline serostatus (the strongest predictor of a protective antibody response) as well as age and sex.
Overall, the antibody titers for the B vaccine component were significantly lower than for the A components in both seronegative and seropositive children, but this finding was consistent with data from other vaccine studies, the researchers noted.
Because baseline serostatus is not easily determined and serologic testing before vaccination is not practical, the study confirms the need for two doses of TIV in previously unvaccinated 5− to 8-year-olds, Dr. Kathryn M. Edwards and Dr. Marie R. Griffin of Vanderbilt University in Nashville, Tenn., said in an editorial (J. Infect. Dis. 2006;194:1027–9).
The children received two 0.5-mL shots of TIV 2 weeks apart. Serum samples were taken at baseline, at 4 weeks after the first dose (before the second dose was given), and at 4 weeks after the second dose. The vaccine was well tolerated among all age groups and in both dosage groups, and no significant differences appeared between the dosage groups in the number of children with redness, swelling, fever, or itching after either one or two doses.
