Immunogenicity and reactogenicity of 1 versus 2 doses of trivalent inactivated influenza vaccine in vaccine-naive 5-8-year-old children

J Infect Dis. 2006 Oct 15;194(8):1032-9. doi: 10.1086/507309. Epub 2006 Sep 11.


Background: Two doses of trivalent inactivated influenza vaccine (TIV) are recommended for children <9 years old receiving vaccine for the first time, but compliance is suboptimal. This study assessed the need for a second dose of TIV in this age group.

Methods: In 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.

Results: Both doses of vaccine were well tolerated. The strongest predictor of a protective antibody response (> or =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 <1:40 for the type B vaccine component, even after 2 doses.

Conclusions: The 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.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antibodies, Viral / blood
  • Child
  • Drug Administration Schedule
  • Female
  • Hemagglutination Inhibition Tests
  • Humans
  • Immunization Schedule*
  • Influenza A Virus, H1N1 Subtype / immunology
  • Influenza A Virus, H3N2 Subtype / immunology
  • Influenza A virus / immunology*
  • Influenza Vaccines / administration & dosage*
  • Influenza Vaccines / adverse effects
  • Influenza, Human / blood
  • Influenza, Human / prevention & control*
  • Injections, Intramuscular
  • Male
  • Patient Compliance
  • Prospective Studies
  • Vaccination / methods*
  • Vaccines, Inactivated / administration & dosage
  • Vaccines, Inactivated / adverse effects
  • Washington


  • Antibodies, Viral
  • Influenza Vaccines
  • Vaccines, Inactivated