Impact of influenza vaccination on mortality risk among the elderly
Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, P.O. Box 85500, 3508 GA, Utrecht, The Netherlands. European Respiratory Journal
(Impact Factor: 7.64).
06/2009; 34(1). DOI: 10.1183/09031936.00190008
Estimates of influenza vaccine effectiveness have mostly been derived from nonrandomised studies and therefore are potentially confounded. The aim of the current study was to estimate influenza vaccine effectiveness in preventing mortality among the elderly, taking both measured and unmeasured confounding into account. Information on patients aged o65 yrs from the computerised Utrecht General Practitioner database on eight influenza epidemic periods and summer periods was pooled to estimate influenza vaccine effectiveness in preventing mortality. Summer periods (during which no effect of vaccination was expected) were used as a reference to control for unmeasured confounding in epidemic periods. After adjustment for measured confounders using multivariable regression analysis, propensity score matching and propensity score regression analysis, influenza vaccination reduced mortality risk (odds ratios (ORs) 0.58 (95% confidence interval (CI) 0.46–0.72), 0.56 (95% CI 0.44–0.71) and 0.56 (95% CI 0.45–0.69), respectively). After additional adjustment for unmeasured confounding (as observed during summer periods), the association between influenza vaccination and mortality risk decreased (OR 0.69 (95% CI 0.52–0.92)). We conclude that after state-of-the-art adjustment for typical confounders such as age, sex and comorbidity status, unmeasured confounding still biased estimates of influenza vaccine effectiveness. After taking unmeasured confounding into account, influenza vaccination is still associated with substantial reduction in mortality risk.
Available from: Ole Wichmann
- "1.45 (0.98-2.14) 1.09 (1.04-1.14) Study Ratio of odds ratios (95%CI) Ratio of odds ratios 0.1 0.5 1 2 10 Pooled Vila-Corcoles et al. (2007) Tessmer et al. (2011) Schembri et al. (2009) Liu et al. (2012) Groenwold et al. (2009) Wong et al. (2012) McGrath et al. (2012) Jackson et al. (2006) Hottes et al. (2011) Campitelli et al. (2011) Bond et al. (2012) 1.08 (0.95-1.24) 1.07 (0.74-1.53) 1.24 (1.10-1.40) 1.10 (0.98-1.23) 1.10 (1.06-1.14) "
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Evidence on influenza vaccine effectiveness (VE) is commonly derived from observational studies. However, these studies are prone to confounding by indication and healthy vaccinee bias. We aimed to systematically investigate these two forms of confounding/bias.
Systematic review of observational studies reporting influenza VE and indicators for bias and confounding. We assessed risk of confounding by indication and healthy vaccinee bias for each study and calculated ratios of odds ratios (crude/adjusted) to quantify the effect of confounder adjustment. VE-estimates during and outside influenza seasons were compared to assess residual confounding by healthy vaccinee effects.
We identified 23 studies reporting on 11 outcomes. Of these, 19 (83 %) showed high risk of bias: Fourteen due to confounding by indication, two for healthy vaccinee bias, and three studies showed both forms of confounding/bias. Adjustment for confounders increased VE on average by 12 % (95 % CI: 7-17 %; all-cause mortality), 9 % (95 % CI: 4-14 %; all-cause hospitalization) and 7 % (95 % CI: 4-10 %; influenza-like illness). Despite adjustment, nine studies showed residual confounding as indicated by significant off-season VE-estimates. These were observed for five outcomes, but more frequently for all-cause mortality as compared to other outcomes (p = 0.03) and in studies which indicated healthy vaccinee bias at baseline (p = 0.01).
Both confounding by indication and healthy vaccinee bias are likely to operate simultaneously in observational studies on influenza VE. Although adjustment can correct for confounding by indication to some extent, the resulting estimates are still prone to healthy vaccinee bias, at least as long as unspecific outcomes like all-cause mortality are used. Therefore, cohort studies using administrative data bases with unspecific outcomes should no longer be used to measure the effects of influenza vaccination.
BMC Infectious Diseases 10/2015; 15(1):429. DOI:10.1186/s12879-015-1154-y · 2.61 Impact Factor
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ABSTRACT: Human seasonal influenza is a large burden of morbidity and mortality for societies, affecting mainly elderly people and those with underlying chronic medical conditions. Annual vaccination of older adults and other risk groups is the most effective measure for reducing morbidity and mortality associated with infection. A 2008 survey showed 40-fold differences between the vaccination coverage in various European Union countries in individuals aged >or=65 years, ranging from less that 2% to more than 80% in the 2006-2007 season, with Poland belonging to the countries with low influenza vaccination coverage. Annual monitoring of the vaccination coverage is crucial for achieving and maintaining high uptake levels. The need to pay for the vaccine out of pocket is a strong factor discouraging vaccination, and there is evidence that reimbursing costs of influenza vaccination influences vaccination coverage. Although annual influenza immunization of healthcare workers is an important method of preventing the nosocomial transmission of influenza and decreasing the exposure of vulnerable patients, worldwide influenza vaccination rates among healthcare personnel are unacceptably low, rarely exceeding 40%. It is important to keep high vaccination coverage among elderly nursing-home residents. More research is needed to clearly establish the effect of dose sparing strategies of influenza vaccination, e.g., via intradermal immunization, on the immune response in elderly recipients. Finally, due to the emergence of the pandemic influenza A (H1N1) 2009 virus and the development of vaccines directed towards it, the upcoming influenza season 2009-2010 will pose a particular challenge to influenza vaccination programs, and will require careful planning.
Polskie archiwum medycyny wewnȩtrznej 10/2009; 119(10):654-9. · 2.12 Impact Factor
Available from: Paul Drinka
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ABSTRACT: Pneumonia is a major cause of morbidity and mortality among nursing home residents. The approach to managing these patients has lacked uniformity because of the paucity of clinical trials, complexity of underlying comorbid diseases, and heterogeneity of administrative structures. The decision to hospitalize nursing home patients with pneumonia varies among institutions depending on staffing level, availability of diagnostic testing, and laboratory support. In the absence of comparative studies, choice of empirical antibiotic therapy continues to be based on expert opinion. Validated prognostic scoring models are needed for risk stratification. Pneumococcal and influenza vaccination are the primary prevention measures. As of January 2010, Medicare no longer pays for consultation codes; thus, practitioners must instead use existing evaluation and management service codes when providing these services.
Chest 12/2010; 138(6):1480-5. DOI:10.1378/chest.10-1135 · 7.48 Impact Factor
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