Effect of yearly vaccinations with live, attenuated, cold-adapted, trivalent, intranasal influenza vaccines on antibody responses in children.
BACKGROUND
The cold-adapted, trivalent influenza vaccine (CAIV-T) may become an option for annual vaccination. However, there is little information regarding the immune response to repeated immunization with CAIV-T.


OBJECTIVE
To determine the antibody response to repeated immunization with CAIV-T and to compare this with the response after the first CAIV-T immunization.


METHODS
Healthy children were offered CAIV-T immunization for 4 consecutive years, and blood samples were taken from a subset in Years 1, 2 and 4. In Year 4, 156 similarly aged children who had not received influenza vaccine previously were immunized with the same CAIV-T.


RESULTS
The H3N2 and B components of the CAIV-T induced high antibody titers in Year 1 that were maintained during 4 years. The H1N1 titers were lower than the H3N2 or B titers. Comparison of the group immunized for 4 consecutive years with the group immunized for the first time revealed the following: (1) before immunization yearly immunized subjects were more likely to be seropositive to each of the three vaccine strains than those immunized for the first time (P < 0.05 for each); (2) after immunization the percentage of seropositive subjects to each of the strains was similar; (3) after immunization titers were higher in the subjects immunized for the first time than those immunized yearly (P < 0.05 for H3N2 and B).


CONCLUSIONS
Yearly vaccination with CAIV-T induced high antibody titers, especially to the H3N2 and B strains in the vaccines. The titers in those immunized with CAIV-T for the first time were higher than in those immunized for 4 consecutive years.
Bernstein
David I
DI
Division of Infectious Diseases, Cincinnati Children's Hospital Medical Center, OH, USA. david.bernstein@chmcc.org
Yan
Lihan
L
Treanor
John
J
Mendelman
Paul M
PM
Belshe
Robert
R
D000281:Administration, Intranasal; D000914:Antibodies, Viral / Q000097:blood*; D002675:Child, Preschool; D003080:Cold Temperature; D006385:Hemagglutination Inhibition Tests / Q000379:methods; D006801:Humans; D007223:Infant; D009980:Influenza A virus / Q000276:immunology; D009981:Influenza B virus / Q000276:immunology; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology / Q000517:prevention & control*; D013997:Time Factors; D014611:Vaccination; D014613:Vaccines, Attenuated / Q000276:immunology; D017778:Vaccines, Combined / Q000276:immunology
D000914:Antibodies, Viral; D007252:Influenza Vaccines; D014613:Vaccines, Attenuated; D017778:Vaccines, Combined