Elsevier

Vaccine

Volume 27, Issue 44, 19 October 2009, Pages 6261-6267
Vaccine

Modeling the effects of influenza vaccination of health care workers in hospital departments

https://doi.org/10.1016/j.vaccine.2009.07.104Get rights and content

Abstract

Nowadays health care worker (HCW) vaccination is widely recommended. Although the benefits of this strategy have been demonstrated in long-term care settings, no studies have been performed in regular hospital departments. We adapt a previously developed model of influenza transmission in a long-term care nursing home department to study the effects of HCW vaccination in hospital wards. We study both the effectiveness and efficiency in reducing the hazard rates of influenza virus infection for patients. Most scenarios under study show a similar or higher impact of hospital HCW vaccination than has been predicted for the long-term care nursing home department. Therefore, it seems justified to extend the recommendations for HCW vaccination, based on results in the long-term care setting, to short-term care settings as well.

Introduction

Trials in long-term care hospital and nursing home departments have shown a beneficial effect of immunizing health care workers (HCWs) against influenza on the mortality among residents during the influenza season [1], [2], [3]. In addition, the attack rates of influenza-like illnesses, general practitioner consultations and hospital admissions associated with influenza were lower in nursing homes with higher HCW vaccine uptake [3]. Influenza vaccination of institutional HCWs in both long-term care and hospital settings, has been widely recommended as part of routine work safety [4]. For regular hospital departments, however, the effects of HCW vaccination have not been demonstrated in clinical trials so far. Hospital and long-term care departments differ in several aspects, such as the patient flow, the type of patients, the visitor frequency and the contact patterns among patients and HCWs. Therefore the effectiveness and efficiency of HCW vaccination may well be different between the two settings.

To investigate whether the positive effects of HCW vaccination demonstrated in long-term care departments can be extrapolated to hospital departments, a modeling study is required. Here, we adapt a previously developed model of influenza transmission in a long-term care nursing home department. With this mathematical model we were able to confirm the expected negative correlation between the HCW vaccination rate and the number of influenza virus infections among patients in nursing home departments [5]. We now use this model, after adaptation for a short-term care environment, to determine the effectiveness and efficiency of HCW vaccination in preventing influenza virus infections among patients in a hospital ward.

Section snippets

Population and model

We adapt a previously developed nursing home model [5] to simulate the occurrence of influenza virus outbreaks in a general hospital ward, such as a pulmonology or internal medicine ward. Here, most patients are elderly or have underlying risk-elevating medical conditions, such as immune-compromising conditions or chronic respiratory diseases that increase their risk of developing secondary complications after infection with influenza. We simulate a 24-bed ward with 15 rooms, with 4, 2 or 1

Results

Vaccination of HCWs can reduce the hazard of influenza virus infection for patients from 0.029 day−1 when no HCWs are vaccinated to 0.016 day−1 when all HCWs are vaccinated (relative risk 0.57) (Fig. 1). These hazard rates translate into expected probabilities of 0.19 and 0.11, respectively, of acquiring influenza virus infection for a susceptible patient during a 7-day stay in the hospital during the influenza season. Compared with a community hazard of 0.0018 day−1, hospital patients have a 16

Discussion

Immunization of HCWs in general hospitals against influenza can reduce the hazard rate of influenza virus infection for patients and is expected to be at least as efficient as vaccination of nursing home personnel [5]. Our simulation model which was extrapolated from a previously developed nursing home model, predicts high attack rates among hospital HCWs and a high daily hazard of infection for patients that is 16 times as high as in the community.

When we compare the effects of HCW vaccination

Acknowledgements

Conflicts of interest statement: No conflicts.

Funding: The study was funded by a grant from the Netherlands Health Care Organization (ZonMw, no. 6120.0015). MJMB is supported by the Netherlands Organization for Scientific Research (VICI NWO Grant 918.76.611). The funders had no role in the study design, data collection and analysis, nor in the decision to publish or in the preparation of the manuscript.

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