Modest Waning of Influenza Vaccine Efficacy and Antibody Titers During the 2007-2008 Influenza Season.
Antibody titers decrease with time following influenza vaccination, raising concerns that vaccine efficacy might wane. However, the relationship between time since vaccination and protection is unclear.



Time-varying vaccine efficacy (VE[t]) was examined in healthy adult participants (age range, 18-49 years) in a placebo-controlled trial of inactivated influenza vaccine (IIV) and live-attenuated influenza vaccine (LAIV) performed during the 2007-2008 influenza season. Symptomatic respiratory illnesses were laboratory-confirmed as influenza. VE(t) was estimated by fitting a smooth function based on residuals from Cox proportional hazards models. Subjects had blood samples collected immediately prior to vaccination, 30 days after vaccination, and at the end of the influenza season for testing by hemagglutination inhibition and neuraminidase inhibition assays.



Overall efficacy was 70% (95% confidence interval [CI], 50%-82%) for IIV and 38% (95% CI, 5%-59%) for LAIV. Statistically significant waning was detected for IIV (P = .03) but not LAIV (P = .37); however, IIV remained significantly efficacious until data became sparse at the end of the season. Similarly, antibody titers against influenza virus hemagglutinin and neuraminidase significantly decreased over the season among IIV recipients.



Both vaccines were efficacious but LAIV less so. IIV efficacy decreased slowly over time, but the vaccine remained significantly efficacious for the majority of the season.
Department of Epidemiology.
Joshua G
JG
Petrie
Department of Epidemiology.
Suzanne E
SE
Ohmit
Department of Epidemiology.
Rachel
R
Truscon
Department of Epidemiology.
Emileigh
E
Johnson
Department of Biostatistics, University of Michigan School of Public Health, Ann Arbor.
Thomas M
TM
Braun
Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia.
Min Z
MZ
Levine
Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland.
Maryna C
MC
Eichelberger
Department of Epidemiology.
Arnold S
AS
Monto
D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000276:immunology*; D005260:Female; D064368:Healthy Volunteers; D006385:Hemagglutination Inhibition Tests / Q000379:methods; D006388:Hemagglutinins / Q000276:immunology; D006801:Humans; D007159:Immunologic Tests / Q000379:methods; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009439:Neuraminidase / Q000276:immunology; D009975:Orthomyxoviridae / Q000276:immunology*; D012621:Seasons; D014611:Vaccination / Q000379:methods; D014613:Vaccines, Attenuated / Q000276:immunology; D015164:Vaccines, Inactivated / Q000276:immunology; D055815:Young Adult
D000914:Antibodies, Viral; D006388:Hemagglutinins; D007252:Influenza Vaccines; D014613:Vaccines, Attenuated; D015164:Vaccines, Inactivated; D009439:Neuraminidase
antibody persistence; efficacy; hemagglutinin; immune correlates; influenza; influenza vaccine; longevity of antibody; neuraminidase; serologic assays; waning