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dc.contributor.authorTricco, Andrea C.
dc.contributor.authorChit, Ayman
dc.contributor.authorSoobiah, Charlene
dc.contributor.authorHallett, David
dc.contributor.authorMeier, Genevieve
dc.contributor.authorChen, Maggie H.
dc.contributor.authorTashkandi, Mariam
dc.contributor.authorBauch, Chris T.
dc.contributor.authorLoeb, Mark 20:30:32 (GMT) 20:30:32 (GMT)
dc.description.abstractBackground: Influenza vaccines are most effective when the antigens in the vaccine match those of circulating strains. However, antigens contained in the vaccines do not always match circulating strains. In the present work we aimed to examine the vaccine efficacy (VE) afforded by influenza vaccines when they are not well matched to circulating strains. Methods: We identified randomized clinical trials (RCTs) through MEDLINE, EMBASE, the Cochrane Library, and references of included RCTs. RCTs reporting laboratory-confirmed influenza among healthy participants vaccinated with antigens of matching and non-matching influenza strains were included. Two independent reviewers screened citations/full-text articles, abstracted data, and appraised risk of bias. Conflicts were resolved by discussion. A random effects meta-analysis was conducted. VE was calculated using the following formula: (1 - relative risk x 100%). Results: We included 34 RCTs, providing data on 47 influenza seasons and 94,821 participants. The live-attenuated influenza vaccine (LAIV) showed significant protection against mismatched (six RCTs, VE 54%, 95% confidence interval (CI) 28% to 71%) and matched (seven RCTs, VE 83%, 95% CI 75% to 88%) influenza strains among children aged 6 to 36 months. Differences were observed between the point estimates for mismatched influenza A (five RCTs, VE 75%, 95% CI 41% to 90%) and mismatched influenza B (five RCTs, VE 42%, 95% CI 22% to 56%) estimates among children aged 6 to 36 months. The trivalent inactivated vaccine (TIV) also afforded significant protection against mismatched (nine RCTs, VE 52%, 95% CI 37% to 63%) and matched (eight RCTs, VE 65%, 95% CI 54% to 73%) influenza strains among adults. Numerical differences were observed between the point estimates for mismatched influenza A (five RCTs, VE 64%, 95% CI 23% to 82%) and mismatched influenza B (eight RCTs, VE 52%, 95% CI 19% to 72%) estimates among adults. Statistical heterogeneity was low (I-2 < 50%) across all meta-analyses, except for the LAIV meta-analyses among children (I-2 = 79%). Conclusions: The TIV and LAIV vaccines can provide cross protection against non-matching circulating strains. The point estimates for VE were different for matching versus non-matching strains, with overlapping CIs.en
dc.description.sponsorshipCanadian Institutes for Health Research/Drug Safety and Effectiveness Network New Investigator Award in Knowledge Synthesisen
dc.publisherBioMed Centralen
dc.rightsAttribution 2.0 Generic*
dc.subjectAntigenic variationen
dc.subjectCross protectionen
dc.subjectInfluenza A virusen
dc.subjectInfluenza B virusen
dc.subjectSystematic reviewen
dc.titleComparing Influenza Vaccine Efficacy Against Mismatched And Matched Strains: A Systematic Review And Meta-Analysisen
dcterms.bibliographicCitationTricco, A. C., Chit, A., Soobiah, C., Hallett, D., Meier, G., Chen, M. H., … Loeb, M. (2013). Comparing influenza vaccine efficacy against mismatched and matched strains: a systematic review and meta-analysis. BMC Medicine, 11(1).
uws.contributor.affiliation1Faculty of Mathematicsen
uws.contributor.affiliation2Applied Mathematicsen

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