ArticlesEffects of influenza vaccination of health-care workers on mortality of elderly people in long-term care: a randomised controlled trial
Introduction
Influenza is one of the leading causes of respiratory infection.1 It remains an important cause of death in elderly people, with most excess mortality in patients older than 65 years.2 Environmental factors play an important part in determining the risk of infection, and grouping of frail elderly people in long-term care creates an environment that is likely to allow rapid spread of influenza infection. Case-control studies have shown that influenza vaccination of elderly people in long-term care is associated with decreased risk of pneumonia and death.3 This strategy is supported by The Chief Medical Officers in the UK and by the Centers for Disease Control in the USA, who recommend influenza vaccination for elderly people who have chronic disease or who are in long-term care.4, 5 However, the protection afforded by vaccination of frail elderly patients is frequently incomplete, probably because of impaired immune function through inability to develop adequate protective circulating antibody concentrations after vaccination.6, 7
Vaccination of health-care workers has been suggested as an additional or alternative strategy to lower rates of nosocomial transmission to patients at high risk of complications. We have found serological evidence of influenza infection in 23% of hospital staff in a winter season.8 The potential is therefore high for influenza to be brought into elderly-care homes by susceptible health-care workers, and for infection to be transmitted to other health-care workers and to patients. In a previous pilot study, we found that vaccination of health-care workers was associated with a decrease in mortality of elderly patients in long-term care from 17% to 10% over a winter season.9
We did a multicentre, randomised, controlled study to find out whether vaccination of health-care workers can lower mortality and the frequency of laboratory-proven influenza infection in elderly patients in long-term-care hospitals.
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Study design
The study was a parallel-group design with cluster randomisation. Clusters were based on 20 UK National Health Service medical long-term-care geriatric hospitals across west and central Scotland. Hospitals were randomly allocated to be offered routine vaccination of health-care workers or not to be offered vaccination. Randomisation of clusters was balanced and stratified for policy for vaccination of patients and size of hospital. Hospitals were paired according to number of beds and policy
Results
1217 health-care workers were employed in the hospitals offered influenza vaccine; 620 (50·9%) were vaccinated (figure 1). The questionnaires from the same sites showed an uptake of 49·8% in respondents (trained and untrained nurses), compared with 4·8% in hospitals not offered vaccine. The questionnaire return rates were estimated to be 68% from nurses in vaccine hospitals and 49% in no-vaccine hospitals.
1437 patients (749 in vaccine hospitals 688 in no-vaccine hospitals) were included in the
Discussion
We achieved a vaccine uptake in health-care workers of about 50%. This proportion is slightly lower than the 60% vaccinated in our previous study,9 but is similar to other vaccination programmes of health-care workers in long-term-care homes in the USA that gave compliance rates of 46–54%.16 Our programme of influenza vaccination was associated with a decrease in mortality among patients. The effects of various possible confounders must, however, be taken into account before this association
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