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Estimating influenza vaccine effectiveness in community-dwelling elderly patients using the instrumental variable analysis method.
Arch Intern Med 2012; 172(6):484-91AI

Abstract

BACKGROUND

Estimates of influenza vaccine effectiveness in elderly individuals are largely from observational studies, which are susceptible to bias. Instrumental variable (IV) methods control for overt and hidden biases in observational studies.

METHODS

We used linked health administrative databases in Ontario to examine the association between influenza vaccination and all-cause mortality among community-dwelling individuals older than 65 years for 9 influenza seasons (2000-2001 to 2008-2009). We examined the composite of hospitalization for pneumonia and influenza and all-cause mortality as a secondary outcome. We used logistic regression modeling and IV analysis to remove the effect of selection bias.

RESULTS

We included 12 621 806 person-influenza seasons of observation. Logistic regression produced adjusted odds ratios of 0.67 (95% CI, 0.62-0.72) for all-cause mortality during influenza seasons and 0.85 (0.83-0.86) during post-influenza seasons when influenza is not circulating, suggesting the presence of bias. In contrast, IV analysis yielded adjusted odds ratios of 0.94 (95% CI, 0.84-1.03) during influenza seasons and 1.13 (1.07-1.19) during post-influenza seasons. For the composite of hospitalization for pneumonia and influenza and death, logistic regression produced adjusted odds ratios of 0.74 (95% CI, 0.70-0.78) during influenza seasons and 0.88 (0.87-0.90) during post-influenza seasons, whereas IV analysis produced adjusted odds ratios of 0.86 (95% CI, 0.79-0.92) and 1.02 (0.97-1.06), respectively.

CONCLUSIONS

Influenza vaccination is associated with reductions in the composite of hospitalizations for pneumonia and influenza and all-cause mortality during the influenza season but not mortality alone. Compared with standard modeling, IV analysis appears to produce less-biased estimates of vaccine effectiveness.

Authors+Show Affiliations

Institute for Clinical Evaluative Sciences, 2075 Bayview Ave, Toronto, ON, Canada.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Evaluation Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

22371873

Citation

Wong, Kenny, et al. "Estimating Influenza Vaccine Effectiveness in Community-dwelling Elderly Patients Using the Instrumental Variable Analysis Method." Archives of Internal Medicine, vol. 172, no. 6, 2012, pp. 484-91.
Wong K, Campitelli MA, Stukel TA, et al. Estimating influenza vaccine effectiveness in community-dwelling elderly patients using the instrumental variable analysis method. Arch Intern Med. 2012;172(6):484-91.
Wong, K., Campitelli, M. A., Stukel, T. A., & Kwong, J. C. (2012). Estimating influenza vaccine effectiveness in community-dwelling elderly patients using the instrumental variable analysis method. Archives of Internal Medicine, 172(6), pp. 484-91. doi:10.1001/archinternmed.2011.2038.
Wong K, et al. Estimating Influenza Vaccine Effectiveness in Community-dwelling Elderly Patients Using the Instrumental Variable Analysis Method. Arch Intern Med. 2012 Mar 26;172(6):484-91. PubMed PMID: 22371873.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Estimating influenza vaccine effectiveness in community-dwelling elderly patients using the instrumental variable analysis method. AU - Wong,Kenny, AU - Campitelli,Michael A, AU - Stukel,Thérèse A, AU - Kwong,Jeffrey C, Y1 - 2012/02/27/ PY - 2012/2/29/entrez PY - 2012/3/1/pubmed PY - 2012/5/15/medline SP - 484 EP - 91 JF - Archives of internal medicine JO - Arch. Intern. Med. VL - 172 IS - 6 N2 - BACKGROUND: Estimates of influenza vaccine effectiveness in elderly individuals are largely from observational studies, which are susceptible to bias. Instrumental variable (IV) methods control for overt and hidden biases in observational studies. METHODS: We used linked health administrative databases in Ontario to examine the association between influenza vaccination and all-cause mortality among community-dwelling individuals older than 65 years for 9 influenza seasons (2000-2001 to 2008-2009). We examined the composite of hospitalization for pneumonia and influenza and all-cause mortality as a secondary outcome. We used logistic regression modeling and IV analysis to remove the effect of selection bias. RESULTS: We included 12 621 806 person-influenza seasons of observation. Logistic regression produced adjusted odds ratios of 0.67 (95% CI, 0.62-0.72) for all-cause mortality during influenza seasons and 0.85 (0.83-0.86) during post-influenza seasons when influenza is not circulating, suggesting the presence of bias. In contrast, IV analysis yielded adjusted odds ratios of 0.94 (95% CI, 0.84-1.03) during influenza seasons and 1.13 (1.07-1.19) during post-influenza seasons. For the composite of hospitalization for pneumonia and influenza and death, logistic regression produced adjusted odds ratios of 0.74 (95% CI, 0.70-0.78) during influenza seasons and 0.88 (0.87-0.90) during post-influenza seasons, whereas IV analysis produced adjusted odds ratios of 0.86 (95% CI, 0.79-0.92) and 1.02 (0.97-1.06), respectively. CONCLUSIONS: Influenza vaccination is associated with reductions in the composite of hospitalizations for pneumonia and influenza and all-cause mortality during the influenza season but not mortality alone. Compared with standard modeling, IV analysis appears to produce less-biased estimates of vaccine effectiveness. SN - 1538-3679 UR - https://www.unboundmedicine.com/medline/citation/22371873/Estimating_influenza_vaccine_effectiveness_in_community_dwelling_elderly_patients_using_the_instrumental_variable_analysis_method_ L2 - https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/10.1001/archinternmed.2011.2038 DB - PRIME DP - Unbound Medicine ER -