Elsevier

The Lancet

Volume 355, Issue 9198, 8 January 2000, Pages 93-97
The Lancet

Articles
Effects of influenza vaccination of health-care workers on mortality of elderly people in long-term care: a randomised controlled trial

https://doi.org/10.1016/S0140-6736(99)05190-9Get rights and content

Summary

Background

Vaccination of health-care workers has been claimed to prevent nosocomial influenza infection of elderly patients in long-term care. Data are, however, limited on this strategy. We aimed to find out whether vaccination of healthcare workers lowers mortality and the frequency of virologically proven influenza in such patients.

Methods

In a parallel-group study, health-care workers in 20 long-term elderly-care hospitals (range 44–105 patients) were randomly offered or not offered influenza vaccine (cluster randomisation, stratified for policy for vaccination of patients and hospital size). All deaths among patients were recorded over 6 months in the winter of 1996–97. We selected a random sample of 50% of patients for virological surveillance for influenza, with combined nasal and throat swabs taken every 2 weeks during the epidemic period. Swabs were tested by tissue culture and PCR for influenza viruses A and B.

Findings

Influenza vaccine uptake in health-care workers was 50·9% in hospitals in which they were routinely offered vaccine, compared with 4·9% in those in which they were not. The uncorrected rate of mortality in patients was 102 (13·6%) of 749 in vaccine hospitals compared with 154 (22·4%) of 688 in no-vaccine hospitals (odds ratio 0·58 [95% CI 0·40–0·84], p=0·014). The two groups did not differ for proportions of patients positive for influenza infection (5·4% and 6·7%, respectively); at necropsy, PCR was positive in none of 17 patients from vaccine hospitals and six (20%) of 30 from novaccine hospitals (p=0·055).

Interpretation

Vaccination of health-care workers was associated with a substantial decrease in mortality among patients. However, virological surveillance showed no associated decrease in non-fatal influenza infection in patients.

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.

Section snippets

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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