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


METHODS
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 (I(2) = 4%, P = 0.39 vs. I(2) = 91%, P < 0.01).


CONCLUSIONS
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.
Unit of PharmacoEpidemiology & PharmacoEconomics (PE2), Department of Pharmacy, University of Groningen, A. Deusinglaan 1, 9713 AV, Groningen, The Netherlands; Department of Epidemiology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, Postbus 30 001, 9700 RB Groningen, the Netherlands.
Maryam
M
Darvishian
Unit of PharmacoEpidemiology & PharmacoEconomics (PE2), Department of Pharmacy, University of Groningen, A. Deusinglaan 1, 9713 AV, Groningen, The Netherlands; Department of Epidemiology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, Postbus 30 001, 9700 RB Groningen, the Netherlands.
Giedre
G
Gefenaite
Medical Research Council Biostatistics Unit, Institute of Public Health, University Forvie Site, Robinson Way, Cambridge. UK. CB2 0SR.
Rebecca M
RM
Turner
Unit of PharmacoEpidemiology & PharmacoEconomics (PE2), Department of Pharmacy, University of Groningen, A. Deusinglaan 1, 9713 AV, Groningen, The Netherlands; Toronto Health Economics and Technology Assessment collaborative, University of Toronto, 144 College st. Rm:685, Toronto ON M5S3M2, Canada.
Petros
P
Pechlivanoglou
Department of Respiratory Infections of the Centre for Infectious Disease Control, National Institute for Public Health and the Environment, PO Box 1, 3720 BA Bilthoven, The Netherlands.
Wim
W
Van der Hoek
Department of Epidemiology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, Postbus 30 001, 9700 RB Groningen, the Netherlands.
Edwin R
ER
Van den Heuvel
Unit of PharmacoEpidemiology & PharmacoEconomics (PE2), Department of Pharmacy, University of Groningen, A. Deusinglaan 1, 9713 AV, Groningen, The Netherlands; Department of Epidemiology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, Postbus 30 001, 9700 RB Groningen, the Netherlands. Electronic address: e.hak@rug.nl.
Eelko
E
Hak
D000368:Aged; D000369:Aged, 80 and over; D015982:Bias; D015331:Cohort Studies; D006760:Hospitalization; D006801:Humans; D007252:Influenza Vaccines / Q000008:administration & dosage*; D007251:Influenza, Human / Q000453:epidemiology* / Q000401:mortality / Q000517:prevention & control; D015201:Meta-Analysis as Topic; D064887:Observational Studies as Topic; D016017:Odds Ratio; D017063:Outcome Assessment, Health Care; D012621:Seasons; D035501:Uncertainty
D007252:Influenza Vaccines
Bias adjustment; Community-dwelling elderly; Meta-analysis; Observational studies; Seasonal influenza; Vaccination