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


RESULTS
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 no-vaccine hospitals (p=0.055).


CONCLUSIONS
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.
Carman
W F
WF
Institute of Virology, University of Glasgow, UK.
Elder
A G
AG
Wallace
L A
LA
McAulay
K
K
Walker
A
A
Murray
G D
GD
Stott
D J
DJ
D000368:Aged; D006282:Health Personnel; D006707:Homes for the Aged; D006801:Humans; D017053:Infection Control / Q000379:methods*; D017757:Infectious Disease Transmission, Professional-to-Patient / Q000517:prevention & control; D007251:Influenza, Human / Q000401:mortality* / Q000517:prevention & control*; D008134:Long-Term Care; D016133:Polymerase Chain Reaction; D012606:Scotland; D014611:Vaccination / Q000706:statistics & numerical data*; D000078329:Workforce