Review Article
After adjusting for bias in meta-analysis seasonal influenza vaccine remains effective in community-dwelling elderly,

https://doi.org/10.1016/j.jclinepi.2014.02.009Get rights and content
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Abstract

Objective

To compare the performance of the bias-adjusted meta-analysis to the conventional meta-analysis assessing seasonal influenza vaccine effectiveness among community-dwelling elderly aged 60 years and older.

Study Design and Setting

Systematic literature search revealed 14 cohort studies that met inclusion and exclusion criteria. Laboratory-confirmed influenza, influenza-like illness, hospitalization from influenza and/or pneumonia, and all-cause mortality were study outcomes. Potential biases were identified using bias checklists. The magnitude and uncertainty of biases were assessed by expert opinion. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using random effects model.

Results

After incorporating biases, overall effect estimates regressed slightly toward no effect, with the largest relative difference between conventional and bias-adjusted ORs for laboratory-confirmed influenza (OR, 0.18; 95% CI: 0.01, 3.00 vs. OR, 0.23; 95% CI: 0.03, 2.04). In most of the studies, CIs widened reflecting uncertainties about the biases. The between-study heterogeneity reduced considerably with the largest reduction for all-cause mortality (I2 = 4%, P = 0.39 vs. I2 = 91%, P < 0.01).

Conclusion

This case study showed that after addressing potential biases influenza vaccine was still estimated effective in preventing hospitalization from influenza and/or pneumonia and all-cause mortality. Increasing the number of assessors and incorporating empirical evidence might improve the new bias-adjustment method.

Keywords

Meta-analysis
Bias adjustment
Observational studies
Seasonal influenza
Vaccination
Community-dwelling elderly

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This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Funding: The current work is funded by the University of Groningen.

Conflict of interest: All authors declare to have no conflict of interest with regard to the work.