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. 2011 Jan 1;203(1):32-9.
doi: 10.1093/infdis/jiq014.

Age-specific effectiveness of an oil-in-water adjuvanted pandemic (H1N1) 2009 vaccine against confirmed infection in high risk groups in England

Nick Andrews  1 , Pauline Waight, Chee-Fu Yung, Elizabeth Miller
Affiliations

Age-specific effectiveness of an oil-in-water adjuvanted pandemic (H1N1) 2009 vaccine against confirmed infection in high risk groups in England

Nick Andrews et al. J Infect Dis. .

Abstract

Background: The use of a squalene-containing (AS03) pandemic vaccine for high-risk groups in England allowed vaccine effectiveness (VE) of such novel oil-in-water adjuvanted vaccine to be evaluated.

Methods: Cases of laboratory-confirmed pandemic (H1N1)2009 influenza in England between November 2009 and January 2010 were followed up for history of pandemic (H1N1)2009 or 2009/10 seasonal influenza vaccination and relevant comorbidities. Controls were patients similarly tested but negative for the virus. We estimated pandemic (H1N1)2009 VE from the relative reduction in the odds of confirmed pandemic (H1N1)2009 infection between vaccinated and unvaccinated individuals after adjustment for confounders.

Results: A total of 933 cases and 1220 controls were analyzed. VE from ≥ 14 days was 62% (95% CI 33% to 78%) with protection from 7 to 13 days post-vaccination (59%, 95% CI 12% to 81%). VE from ≥ 14 days differed by age (P = .03) being 77% (11% to 94%) in children <10 years, 100% (80% to 100%) in 10-24-year olds, 22% (-153% to 76%) in 25-49-year olds, and 41% (-71% to 80%) in 50-plus-year-olds.

Conclusion: Use of oil-in-water adjuvant contributed to a high VE with reduced antigen dosage in children and young adults. Our VE estimate supports the serological correlates of protection used for licensure in these age groups. However, the immunological basis of disappointing VE in older adults merits investigation.

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Figures

Figure 1.
Figure 1.
Distribution by week and year of illness onset and proportion vaccinated for the PCR swab positives and negatives in the vaccine effectiveness analyses. Also shown is the cumulative pandemic (H1N1) 2009 vaccine coverage in risk groups in England by week of administration, and estimated distribution of cases* in the second wave by week of onset from week 35, 2009 to week 7, 2010. * Estimated from influenza-like illness reports from general practice data (Q surveillance) combined with pandemic (H1N1) 2009 positivity rates from routine swabbing of influenza-like illness cases.
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