Incidence of Influenza in Healthy Adults and Healthcare Workers: A Systematic Review and Meta-Analysis

Suryaprakash Sambhara,Stefan P Kuster,Anne Wormsbecker,Allison Mcgeer,Po-Po Lam,Agnes Tong,Prakesh S Shah,Brenda L Coleman

doi:10.1371/journal.pone.0026239

Suryaprakash Sambhara, Stefan P Kuster + Show 6 more

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https://doi.org/10.1371/journal.pone.0026239

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Abstract

BackgroundWorking in healthcare is often considered a risk factor for influenza; however, this risk has not been quantified. We aimed to systematically review evidence describing the annual incidence of influenza among healthy adults and healthcare workers (HCWs).Methods and FindingsWe searched OVID MEDLINE (1950 to 2010), EMBASE (1947 to 2010) and reference lists of identified articles. Observational studies or randomized trials reporting full season or annual influenza infection rates for healthy, working age adult subjects and HCWs were included. Influenza infection was defined as a four-fold rise in antibody titer, or positive viral culture or polymerase chain reaction.From 24,707 citations, 29 studies covering 97 influenza seasons with 58,245 study participants were included. Pooled influenza incidence rates (IR) (95% confidence intervals (CI)) per 100 HCWs per season and corresponding incidence rate ratios (IRR) (95% CI) as compared to healthy adults were as follows. All infections: IR 18.7 (95% CI, 15.8 to 22.1), IRR 3.4 (95% CI, 1.2 to 5.7) in unvaccinated HCWs; IR 6.5 (95% CI, 4.6 to 9.1), IRR 5.4 (95% CI, 2.8 to 8.0) in vaccinated HCWs. Symptomatic infections: IR 7.5 (95% CI, 4.9 to 11.7), IRR 1.5 (95% CI, 0.4 to 2.5) in unvaccinated HCWs, IR 4.8 (95% CI, 3.2 to 7.2), IRR 1.6 (95% CI, 0.5 to 2.7) in vaccinated HCWs.ConclusionsCompared to adults working in non-healthcare settings, HCWs are at significantly higher risk of influenza.

Highlights

One frequently postulated risk factor for influenza infection is being a healthcare provider [1]
We aimed to systematically review evidence describing the annual incidence of influenza among healthy adults and healthcare workers (HCWs), and to evaluate the hypothesis that influenza incidence rates are higher in HCWs than in other healthy, community-dwelling adults
Our systematic review and meta-analyses of influenza incidence in HCWs and other healthy adults suggests that HCWs are at higher risk for influenza infection as compared to healthy adults working in non-healthcare settings

Summary

Introduction

One frequently postulated risk factor for influenza infection is being a healthcare provider [1]. One study during a single season has prospectively assessed the risk of serologically proven influenza infection associated with HCW status in a large, multicenter cohort. Many studies have reported rates of influenza in working adults, and others have reported rates among HCWs. We aimed to systematically review evidence describing the annual incidence of influenza among healthy adults and HCWs, and to evaluate the hypothesis that influenza incidence rates are higher in HCWs than in other healthy, community-dwelling adults. We aimed to systematically review evidence describing the annual incidence of influenza among healthy adults and healthcare workers (HCWs)

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