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. 2012 Oct;55(7):951-9.
doi: 10.1093/cid/cis574. Epub 2012 Jul 25.

Effectiveness of seasonal influenza vaccines in the United States during a season with circulation of all three vaccine strains

John J Treanor  1 , H Keipp Talbot, Suzanne E Ohmit, Laura A Coleman, Mark G Thompson, Po-Yung Cheng, Joshua G Petrie, Geraldine Lofthus, Jennifer K Meece, John V Williams, Lashondra Berman, Caroline Breese Hall, Arnold S Monto, Marie R Griffin, Edward Belongia, David K Shay; US Flu-VE Network
Collaborators, Affiliations

Effectiveness of seasonal influenza vaccines in the United States during a season with circulation of all three vaccine strains

John J Treanor et al. Clin Infect Dis. 2012 Oct.

Abstract

Background: Influenza vaccines may be reformulated annually because of antigenic drift in influenza viruses. However, the relationship between antigenic characteristics of circulating viruses and vaccine effectiveness (VE) is not well understood. We conducted an assessment of the effectiveness of US influenza vaccines during the 2010-2011 season.

Methods: We performed a case-control study comparing vaccination histories between subjects with acute respiratory illness with positive real-time reverse transcription polymerase chain reaction for influenza and influenza test-negative controls. Subjects with acute respiratory illness of ≤7 days duration were enrolled in hospitals, emergency departments, or outpatient clinics in communities in 4 states. History of immunization with the 2010-2011 vaccine was ascertained from vaccine registries or medical records. Vaccine effectiveness was estimated in logistic regression models adjusted for study community, age, race, insurance status, enrollment site, and presence of a high-risk medical condition.

Results: A total of 1040 influenza-positive cases and 3717 influenza-negative controls were included from the influenza season, including 373 cases of influenza A(H1N1), 334 cases of influenza A(H3N2), and 333 cases of influenza B. Overall adjusted VE was 60% (95% confidence interval [CI], 53%-66%). Age-specific VE estimates ranged from 69% (95% CI, 56%-77%) in children aged 6 months-8 years to 38% (95% CI, -16% to 67%) in adults aged ≥65 years.

Conclusions: The US 2010-2011 influenza vaccines were moderately effective in preventing medically attended influenza during a season when all 3 vaccine strains were antigenically similar to circulating viruses. Continued monitoring of influenza vaccines in all age groups is important, particularly as new vaccines are introduced.

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Figures

Figure 1.
Figure 1.
Numbers of influenza-positive acute respiratory illness cases (red bars) and influenza reverse transcription polymerase chain reaction–negative acute respiratory illness controls (blue bars) by week of enrollment.
Figure 2.
Figure 2.
Numbers of subjects enrolled and excluded from the final analysis of vaccine effectiveness. PCR, polymerase chain reaction.
See this image and copyright information in PMC

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