Researchers have called for improved delivery of influenza vaccination to the elderly, following a study showing significant reductions in hospitalisation and death in this "high-priority" group.
The study examined the effectiveness of influenza vaccination over ten seasons (1990-2000). The investigators pooled data from 18 cohorts of community-dwelling elderly members of health maintenance organisations (HMOs) to estimate the effects of the vaccine on hospitalisations for pneumonia or influenza, and on death. The analysis accounted for confounders such as age and pre-existing medical conditions.
A total of 713,872 person-seasons were included. On average, vaccination was associated with a 27% reduction in the risk of hospitalisation for pneumonia or influenza, and a 48% reduction in the risk of death.
Most previous studies on the effectiveness of influenza vaccine have been confined to one to two flu seasons, which provided an incomplete picture of the benefits of vaccination over longer periods. This study gave a longer-term perspective, and included data from two years where there was a relatively poor antigenic match between the circulating viruses and the vaccine strains. In these seasons, there was a smaller reduction in risk of death (37%), compared to a 52% reduction in the seasons where it was a good match.
Vaccination rates in elderly Americans were below the Advisory Committee on Immunization Practices’ goal of 90% by the year 2010. The researchers called for renewed efforts to improve the delivery of influenza vaccines in this population, and improve vaccination rates. "Hospitalisations and deaths will be prevented if we can succeed," they said.
Reference
Nichol, K. Nordin, J. et al. 2007, 'Effectiveness of influenza vaccine in the community-dwelling elderly.' New England Journal of Medicine vol.357, pp.1373-1381.
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