A rapid evidence appraisal of influenza vaccination in health workers: An important policy in an area of imperfect evidence

Abstract

Introduction The World Health Organization recommends vaccination of health workers (HWs) against influenza, but low uptake is intransigent. We conducted a Rapid Evidence Appraisal on: the risk of influenza in HWs, transmission risk from HWs to patients, the benefit of HW vaccination, and strategies for improving uptake. We aimed to capture a ‘whole-of-system’ perspective to consider possible benefits for HWs, employers and patients. Methods We executed a comprehensive search of the available literature published from 2006 to 2018 in the English language. We developed search terms for seven separate questions following the PICO framework (population, intervention, comparators, outcomes) and queried nine databases. Results Of 3784 publications identified, 52 met inclusion criteria. Seven addressed HW influenza risk, of which four found increased risk; 15 addressed influenza vaccine benefit to HWs or their employers, of which 10 found benefit; 11 addressed influenza transmission from HWs to patients, of which 6 found evidence for transmission; 12 unique studies addressed whether vaccinating HWs produced patient benefit, of which 9 concluded benefits accrued. Regarding the number of HWs needed to vaccinate (NNV) to deliver patient benefit, NNV estimates ranged from 3 to 36,000 but were in significant disagreement. Fourteen studies provided insights on strategies to improve uptake; the strongest evidence was for mandatory vaccination. Conclusions The evidence on most questions related to influenza vaccination in HWs is mixed and often of low-quality. Substantial heterogeneity exists in terms of study designs and settings, making comparison between studies difficult. Notwithstanding these limitations, a majority of studies suggests that influenza vaccination benefit HWs and their employers; and HWs are implicated in transmission events. The effects of vaccinating HWs on patient morbidity and mortality may include reductions in all-cause mortality and influenza-like illness (ILI). Taken together, the evidence suggests that HW vaccination is an important policy for HWs themselves, their employers, and their patients.

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“…HCWs are at increased risk of influenza exposure/infection and play an important role in spreading the virus during hospital outbreaks, as transmission can occur before symptoms. The number (of HCWs) needed to vaccinate to ensure a benefit to one patient ranges from 3 to 50 [83]. This benefit is most obvious in long-term care facilities hosting highrisk elderly patients.…”

“…This benefit is most obvious in long-term care facilities hosting highrisk elderly patients. It is estimated that 60% of infections could be prevented if all HCWs in these settings were vaccinated [83]. However, acceptance of annual influenza vaccination is challenging.…”

“…However, acceptance of annual influenza vaccination is challenging. A systematic review showed that the strongest motivation for HCWs to get vaccinated was to protect themselves (or their families), and not their patients [83]; the strongest barriers against vaccination were lack of confidence about disease severity or vaccine effectiveness, concerns about vaccine safety, and lack of professional or ethical obligation to get vaccinated. A high level of misinformation on influenza disease and vaccination exists [84].…”

“…Mandatory vaccination remains the most successful intervention to increase vaccine uptake but is frequently not acceptable or feasible. "Soft-mandate" including opt-out programs, such as requiring mask use during the whole flu season for those who decline vaccination, may be an acceptable alternative [83].…”

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“…Their immune response however is less adequate which makes the vaccination less effective [7][8][9][10][11]. This means that these individuals may need additional protection, for example, by vaccinating healthcare workers, because they are in close contact with patients highly susceptible to influenza [12][13][14][15][16][17]. Unfortunately, the vaccination rate of healthcare workers is generally low in the Netherlands.…”