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Epidemiology. 2015 Oct 1. [Epub ahead of print]
Quantifying protection against influenza virus infection measured by hemagglutination-inhibition assays in vaccine trials.
Zhao X1, Fang VJ, Ohmit SE, Monto AS, Cook AR, Cowling BJ.
Author information
Abstract
BACKGROUND:
Correlations between hemagglutination-inhibition titers (hereafter 'titers') and protection against infection have been identified in historical studies. However, limited information is available about the dynamics of how titer influences protection.
METHODS:
Titers were measured in randomized, placebo-controlled vaccine trials in Hong Kong (HK) among paediatrics during September 2009-December 2010 and the United States (US) among adults during Oct 2007 - April 2008. Intermediate unobserved titers were imputed using three interpolation methods. As participants were recruited at different times leading to varying exposure to infection relative to entry, amodified proportional hazards model was developed to account for staggered entry into the studies and to quantify the correlation of titers with protection against influenza infections, adjusting for waning in titers. The model was fitted using Markov chain Monte Carlo and importance sampling.
RESULTS:
A titer of 1:40 was associated with a reduced infection risk of40%-70% relative to a titer of 1:10, depending on the circulating strain; the corresponding protection associated witha titer of 1:80 was 54%-84%. Results were robust across interpolation methods. The trivalent inactivated vaccine reduced cumulative incidence of influenza B and influenza A(H3N2) infections by 6 percentage points (pp) (95% credible interval (CrI): 2pp, 10pp) and 1pp (95% CrI: 0.3pp, 2pp) respectively, but not for influenza A(H1N1)pdm09. The live attenuated vaccine showed little efficacy against influenza A(H3N2) infections.
CONCLUSIONS:
Titers are correlated with protection against influenza infections. The trivalent inactivated vaccine can reduce the risk of influenza A(H3N2) and influenza B infections in the community.
PMID: 26427723 [PubMed - as supplied by publisher]
Quantifying protection against influenza virus infection measured by hemagglutination-inhibition assays in vaccine trials.
Zhao X1, Fang VJ, Ohmit SE, Monto AS, Cook AR, Cowling BJ.
Author information
Abstract
BACKGROUND:
Correlations between hemagglutination-inhibition titers (hereafter 'titers') and protection against infection have been identified in historical studies. However, limited information is available about the dynamics of how titer influences protection.
METHODS:
Titers were measured in randomized, placebo-controlled vaccine trials in Hong Kong (HK) among paediatrics during September 2009-December 2010 and the United States (US) among adults during Oct 2007 - April 2008. Intermediate unobserved titers were imputed using three interpolation methods. As participants were recruited at different times leading to varying exposure to infection relative to entry, amodified proportional hazards model was developed to account for staggered entry into the studies and to quantify the correlation of titers with protection against influenza infections, adjusting for waning in titers. The model was fitted using Markov chain Monte Carlo and importance sampling.
RESULTS:
A titer of 1:40 was associated with a reduced infection risk of40%-70% relative to a titer of 1:10, depending on the circulating strain; the corresponding protection associated witha titer of 1:80 was 54%-84%. Results were robust across interpolation methods. The trivalent inactivated vaccine reduced cumulative incidence of influenza B and influenza A(H3N2) infections by 6 percentage points (pp) (95% credible interval (CrI): 2pp, 10pp) and 1pp (95% CrI: 0.3pp, 2pp) respectively, but not for influenza A(H1N1)pdm09. The live attenuated vaccine showed little efficacy against influenza A(H3N2) infections.
CONCLUSIONS:
Titers are correlated with protection against influenza infections. The trivalent inactivated vaccine can reduce the risk of influenza A(H3N2) and influenza B infections in the community.
PMID: 26427723 [PubMed - as supplied by publisher]