ReviewEffectiveness of seasonal influenza vaccination in healthcare workers: a systematic review
Introduction
Influenza is a highly contagious viral infection that leads to the abrupt onset of respiratory symptoms. The attack rates of seasonal influenza generally range from 10% to 20% in healthy adults, but can exceed 80% in hospital outbreaks and long term care facilities.1, 2, 3, 4, 5 The transmission of influenza A (H1N1) causing the pandemic in 2009 was even higher, as the majority of population did not have such immunity to this strain, especially the younger age group.6 A review of the influenza pandemic in 2009 suggested that 15–45% of the world’s population has already become infected by this newly emergent strain.7 Although influenza is mostly a mild and self-limiting illness, it can pose a significant health risk to vulnerable groups.8, 9 Vaccination has been demonstrated to be the most effective way to prevent influenza-related complications among high risk populations such as children, elderly and patients with comorbidity.10, 11, 12 Healthcare workers (HCWs) are also a target for the influenza vaccination because they may serve as the vector for transmitting influenza virus to patients after they become infected from either the community or healthcare setting.2, 13, 14, 15, 16
Despite general consensus and recommendations for influenza vaccination of HCWs, vaccine coverage among HCWs has remained low and is far below the desired level to achieve herd immunity.17, 18, 19, 20 The low vaccination rate among HCWs may be associated with doubts over the effectiveness of the vaccine and fear of its adverse effects.21 Negative information regarding safety can be an influencing factor for HCWs to reject newly developed vaccines, such as the pandemic H1N1 vaccine.22 Although several systematic reviews have already evaluated the effectiveness of influenza vaccine in different groups of high risk persons, no review has yet focused on the outcomes in HCWs. Evidence of such effectiveness is important to increase the confidence of HCWs in influenza vaccines and provide a rational backdrop for the future development of vaccination policies. This systematic review evaluates the effectiveness of influenza vaccines in terms of (i) preventing laboratory-confirmed influenza infections, (ii) preventing influenza-like illness (ILI), and (iii) reducing working days lost among HCWs. This review also aims to determine the adverse effects among HCWs after receiving the influenza vaccine.
Section snippets
Search strategy
The authors used 22 electronic healthcare databases and internet resources to search for eligible studies (Box 1). All databases were searched from the date of their launch up to 14 March 2011. Searches were conducted using a combination of the following keywords with relevant MeSH or abbreviated terms if applicable. The keywords included influenza vaccines (influenza, human/prevention and control; influenza vaccin*; inoculation; immuni*), effectiveness (efficacy), health personnel (medical
Characteristics of the studies
In total, 5090 studies were identified using the predefined search strategy and keywords. Of these, 5070 were excluded after the titles and abstracts of the articles had been reviewed. Of the remaining 20 studies, 17 were eventually excluded after a full review of the report, because of irrelevant outcome measures or study designs (Table I).25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41 Three RCTs meeting the inclusion criteria were finally identified (Table II).15, 42, 43
Discussion
This is the first systematic review evaluating the effectiveness of influenza vaccinations on HCWs by comparing laboratory-confirmed influenza infections, ILI, working days lost, and adverse effects between vaccinated and unvaccinated HCWs. An extensive search revealed only three RCTs conducted in hospital settings that fulfilled the selection criteria. All of these studies used trivalent inactivated parenteral seasonal influenza vaccine, and they involved a total of 967 HCWs. A pooled analysis
Conflict of interest statement
None declared.
Funding sources
None.
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Influenza vaccine effectiveness within prospective cohorts of healthcare personnel in Israel and Peru 2016–2019
2021, VaccineCitation Excerpt :Effective influenza vaccines could potentially reduce missed work and mitigate HCP shortages during influenza seasons [2,4] and possibly prevent secondary transmissions of the virus to patients [5]. Yet, data on influenza vaccine effectiveness (IVE) in preventing laboratory-confirmed influenza illness among HCP are limited [2,6]. The only randomized controlled trial of influenza vaccine efficacy among HCP relied on serologic outcomes [7], which often miss infections among vaccinees thereby inflating IVE estimates [8].
The Health Belief Model in predicting healthcare workers' intention for influenza vaccine uptake in Jordan
2020, VaccineCitation Excerpt :These rates are comparable to the global vaccination rates and the median coverage of 28.2% in the EMR countries [2,14,24]. It is striking that being a physician was not associated with a higher likelihood of intending to receive the influenza vaccine, despite the presumably greater knowledge of the vaccine among physicians compared to the other categories of HCWs [2,25–28]. An explanation is highlighted in the literature where the increased knowledge of HCWs is offset by misperceptions varying according to the category of HCWs [2,25–28].
Could enhanced influenza and pneumococcal vaccination programs help limit the potential damage from SARS-CoV-2 to fragile health systems of southern hemisphere countries this winter?
2020, International Journal of Infectious DiseasesA rapid evidence appraisal of influenza vaccination in health workers: An important policy in an area of imperfect evidence
2019, Vaccine: XCitation Excerpt :The study concluded that vaccination provided a protective effect in HWs and deemed vaccination programs as cost-saving. The widely-cited studies by Kliner et al. [66] and Kuster et al. [64] were included in the appraisal by Dini et al who identified 6 reviews relevant to this question [64,66–70] and also concluded that vaccination was protective and potentially cost-saving in HWs [11]. Two contradictory RCTs included a Malaysian study that [28] found reduced absenteeism (12 days vs. 52 in the control group, p = 0.002) and ILI (reduced by 52.6%, p = 0.002) due to vaccination, using all self-reported outcomes.
Do we have enough evidence how seasonal influenza is transmitted and can be prevented in hospitals to implement a comprehensive policy?
2016, VaccineCitation Excerpt :A Cochrane review of vaccinating healthy adults age 18–60 found the NNV currently to prevent one case of laboratory-proven influenza for inactivated vaccines is 71 (95%CI 64%, 80%) [13]. Secondly, the Cochrane review of HCW vaccination identified only three RCTs [23] and for the one which reported laboratory-proven influenza the VE was 88% (95%CI 59–96), p = 0.0005 [24]. Thirdly, the Cochrane review of vaccinating HCWs to prevent influenza in elderly patients they care for in nursing homes identified only three RCTs and no conclusions could be drawn due to performance and detection bias [25].