Live and inactivated influenza vaccines induce similar humoral responses, but only live vaccines induce diverse T-cell responses in young children

J Infect Dis. 2011 Sep 15;204(6):845-53. doi: 10.1093/infdis/jir436. Epub 2011 Aug 15.


Background: Two doses of either trivalent live attenuated or inactivated influenza vaccines (LAIV and TIV, respectively) are approved for young children (≥ 24 months old for LAIV and ≥ 6 months old for TIV) and induce protective antibody responses. However, whether combinations of LAIV and TIV are safe and equally immunogenic is unknown. Furthermore, LAIV is more protective than TIV in children for unclear reasons.

Methods: Children 6-35 months old were administered, 1 month apart, 2 doses of either TIV or LAIV, or combinations of LAIV and TIV in both prime/boost sequences. Influenza-specific antibodies were measured by hemagglutination inhibition (HAI), and T cells were studied in flow cytometric and functional assays. Highly conserved M1, M2, and NP peptides predicted to be presented by common HLA class I and II were used to stimulate interferon-γ enzyme-linked immunospot responses.

Results: All LAIV and/or TIV combinations were well tolerated and induced similar HAI responses. In contrast, only regimens containing LAIV induced influenza-specific CD4(+), CD8(+), and γδ T cells, including T cells specific for highly conserved influenza peptides.

Conclusions: Prime/boost combinations of LAIV and TIV in young children were safe and induced similar protective antibodies. Only LAIV induced CD4(+), CD8(+), and γδ T cells relevant for broadly protective heterosubtypic immunity.

Clinical trials registration: NCT00231907.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antibodies, Viral / blood*
  • Child, Preschool
  • Enzyme-Linked Immunospot Assay
  • Female
  • Flow Cytometry
  • Hemagglutination Inhibition Tests
  • Humans
  • Immunization, Secondary / adverse effects
  • Immunization, Secondary / methods
  • Infant
  • Influenza Vaccines / administration & dosage
  • Influenza Vaccines / adverse effects
  • Influenza Vaccines / immunology*
  • Influenza, Human / prevention & control*
  • Male
  • T-Lymphocytes / immunology*
  • Vaccination / adverse effects
  • Vaccination / methods
  • Vaccines, Attenuated / administration & dosage
  • Vaccines, Attenuated / adverse effects
  • Vaccines, Attenuated / immunology
  • Vaccines, Inactivated / administration & dosage
  • Vaccines, Inactivated / adverse effects
  • Vaccines, Inactivated / immunology


  • Antibodies, Viral
  • Influenza Vaccines
  • Vaccines, Attenuated
  • Vaccines, Inactivated

Associated data