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Effectiveness of influenza vaccine in the community-dwelling elderly.
N Engl J Med 2007; 357(14):1373-81NEJM

Abstract

BACKGROUND

Reliable estimates of the effectiveness of influenza vaccine among persons 65 years of age and older are important for informed vaccination policies and programs. Short-term studies may provide misleading pictures of long-term benefits, and residual confounding may have biased past results. This study examined the effectiveness of influenza vaccine in seniors over the long term while addressing potential bias and residual confounding in the results.

METHODS

Data were pooled from 18 cohorts of community-dwelling elderly members of one U.S. health maintenance organization (HMO) for 1990-1991 through 1999-2000 and of two other HMOs for 1996-1997 through 1999-2000. Logistic regression was used to estimate the effectiveness of the vaccine for the prevention of hospitalization for pneumonia or influenza and death after adjustment for important covariates. Additional analyses explored for evidence of bias and the potential effect of residual confounding.

RESULTS

There were 713,872 person-seasons of observation. Most high-risk medical conditions that were measured were more prevalent among vaccinated than among unvaccinated persons. Vaccination was associated with a 27% reduction in the risk of hospitalization for pneumonia or influenza (adjusted odds ratio, 0.73; 95% confidence interval [CI], 0.68 to 0.77) and a 48% reduction in the risk of death (adjusted odds ratio, 0.52; 95% CI, 0.50 to 0.55). Estimates were generally stable across age and risk subgroups. In the sensitivity analyses, we modeled the effect of a hypothetical unmeasured confounder that would have caused overestimation of vaccine effectiveness in the main analysis; vaccination was still associated with statistically significant--though lower--reductions in the risks of both hospitalization and death.

CONCLUSIONS

During 10 seasons, influenza vaccination was associated with significant reductions in the risk of hospitalization for pneumonia or influenza and in the risk of death among community-dwelling elderly persons. Vaccine delivery to this high-priority group should be improved.

Authors+Show Affiliations

Medicine Service and Center for Chronic Disease Outcomes Research, Minneapolis Veterans Affairs Medical Center and University of Minnesota, Minneapolis 55417, USA. nicho014@umn.eduNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Evaluation Studies
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

17914038

Citation

Nichol, Kristin L., et al. "Effectiveness of Influenza Vaccine in the Community-dwelling Elderly." The New England Journal of Medicine, vol. 357, no. 14, 2007, pp. 1373-81.
Nichol KL, Nordin JD, Nelson DB, et al. Effectiveness of influenza vaccine in the community-dwelling elderly. N Engl J Med. 2007;357(14):1373-81.
Nichol, K. L., Nordin, J. D., Nelson, D. B., Mullooly, J. P., & Hak, E. (2007). Effectiveness of influenza vaccine in the community-dwelling elderly. The New England Journal of Medicine, 357(14), pp. 1373-81.
Nichol KL, et al. Effectiveness of Influenza Vaccine in the Community-dwelling Elderly. N Engl J Med. 2007 Oct 4;357(14):1373-81. PubMed PMID: 17914038.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effectiveness of influenza vaccine in the community-dwelling elderly. AU - Nichol,Kristin L, AU - Nordin,James D, AU - Nelson,David B, AU - Mullooly,John P, AU - Hak,Eelko, PY - 2007/10/5/pubmed PY - 2007/10/10/medline PY - 2007/10/5/entrez SP - 1373 EP - 81 JF - The New England journal of medicine JO - N. Engl. J. Med. VL - 357 IS - 14 N2 - BACKGROUND: Reliable estimates of the effectiveness of influenza vaccine among persons 65 years of age and older are important for informed vaccination policies and programs. Short-term studies may provide misleading pictures of long-term benefits, and residual confounding may have biased past results. This study examined the effectiveness of influenza vaccine in seniors over the long term while addressing potential bias and residual confounding in the results. METHODS: Data were pooled from 18 cohorts of community-dwelling elderly members of one U.S. health maintenance organization (HMO) for 1990-1991 through 1999-2000 and of two other HMOs for 1996-1997 through 1999-2000. Logistic regression was used to estimate the effectiveness of the vaccine for the prevention of hospitalization for pneumonia or influenza and death after adjustment for important covariates. Additional analyses explored for evidence of bias and the potential effect of residual confounding. RESULTS: There were 713,872 person-seasons of observation. Most high-risk medical conditions that were measured were more prevalent among vaccinated than among unvaccinated persons. Vaccination was associated with a 27% reduction in the risk of hospitalization for pneumonia or influenza (adjusted odds ratio, 0.73; 95% confidence interval [CI], 0.68 to 0.77) and a 48% reduction in the risk of death (adjusted odds ratio, 0.52; 95% CI, 0.50 to 0.55). Estimates were generally stable across age and risk subgroups. In the sensitivity analyses, we modeled the effect of a hypothetical unmeasured confounder that would have caused overestimation of vaccine effectiveness in the main analysis; vaccination was still associated with statistically significant--though lower--reductions in the risks of both hospitalization and death. CONCLUSIONS: During 10 seasons, influenza vaccination was associated with significant reductions in the risk of hospitalization for pneumonia or influenza and in the risk of death among community-dwelling elderly persons. Vaccine delivery to this high-priority group should be improved. SN - 1533-4406 UR - https://www.unboundmedicine.com/medline/citation/17914038/Effectiveness_of_influenza_vaccine_in_the_community_dwelling_elderly_ L2 - http://www.nejm.org/doi/full/10.1056/NEJMoa070844?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -