Effectiveness of Seasonal Influenza Vaccines in the United States During a Season With Circulation of All Three Vaccine Strains.
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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ABSTRACT: Rapid, accurate, and cost-effective methods to identify the cause of respiratory tract infections are needed to maximize clinical benefit. Outpatients with acute respiratory illness were tested for influenza using a singleplex reverse transcriptase polymerase chain reaction (SRT-PCR) method. A multiplex RT-PCR (MRT-PCR) method tested for influenza and 17 other viruses and was compared with SRT-PCR using chi-square tests. Among 935 patients, 335 (36%) tested positive for influenza A and influenza B using SRT-PCR. Using MRT-PCR, 320 (34.2%) tested positive for influenza A and influenza B. This study supports MRT-PCR as a comparable method for detecting influenza among patients seeking outpatient care for acute respiratory illnesses.Advances in Virology 01/2014; 2014:274679.
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ABSTRACT: Background Cost and quality-adjusted life-years (QALYs) gained by quadrivalent influenza vaccine (QIV) versus trivalent influenza vaccine (TIV) in Hong Kong elderly were estimated over 9 seasons.MethodsTIV-unmatched influenza B infection rates with QIV versus TIV were estimated by an epidemiology model. Model parameters included percentages of influenza B lineages in circulation, influenza B-associated hospital admission, age-specific population, vaccine coverage and effectiveness. Incremental cost per QALY gained (ICER) by QIV versus TIV were estimated from Hong Kong¿s societal perspective.ResultsMean reduction in influenza B infection rate was 191.3 (95%CI 45.1-337.5) per 100,000 population aged ¿65 years. Highest cost savings and QALYs gained by QIV occurred in 2007 with high percentage of TIV-unmatched strain (92.9%) for age groups 65¿79 years (USD266,473 and 22.8 QALYs) and ¿80 years (USD483,461 and 27.3 QALYs). ICERs of QIV were below willingness-to-pay for age group 65¿79 years in 6, 5 and 3 years when QIV cost¿+¿USD1¿+¿USD2 and¿+¿USD5 more than TIV, respectively. For age group ¿80 years, ICERs of QIV were below willingness-to-pay in 7 and 5 years when QIV cost¿+¿USD1 and¿+¿USD5, correspondingly.Conclusions Acceptance of QIV to be cost-effective in Hong Kong elderly was subject to QIV unit cost and percentage of circulating TIV-unmatched influenza B lineages.BMC Infectious Diseases 11/2014; 14(1):618. · 2.56 Impact Factor
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ABSTRACT: Background: The test-negative design is a variant of the case–control study being increasingly used to study influenza vaccine effectiveness (VE). In these studies, patients with influenza-like illness are tested for influenza. Vaccine coverage is compared between those testing positive versus those testing negative to estimate VE. Objectives: We reviewed features in the design, analysis and reporting of 85 published test-negative studies. Data sources: Studies were identified from PubMed, reference lists and email updates. Study eligibility: All studies using the test-negative design reporting end-of-season estimates were included. Study appraisal: Design features that may affect the validity and comparability of reported estimates were reviewed, including setting, study period, source population, case definition, exposure and outcome ascertainment and statistical model. Results: There was considerable variation in the analytic approach, with 68 unique statistical models identified among the studies. Conclusion: Harmonization of analytic approaches may improve the potential for pooling VE estimates.Expert Review of Vaccines 10/2014; · 4.22 Impact Factor