Vaccine
Volume 32, Issue 15, Pages 1641-1774 (26 March 2014)
http://www.sciencedirect.com/science/journal/0264410X/32/15

Methodological quality of systematic reviews on influenza vaccination
Original Research Article
Pages 1678-1684
Cornelius Remschmidt, Ole Wichmann, Thomas Harder
Abstract
Background
There is a growing body of evidence on the risks and benefits of influenza vaccination in various target groups. Systematic reviews are of particular importance for policy decisions. However, their methodological quality can vary considerably.

Objectives
To investigate the methodological quality of systematic reviews on influenza vaccination (efficacy, effectiveness, safety) and to identify influencing factors.

Methods
A systematic literature search on systematic reviews on influenza vaccination was performed, using MEDLINE, EMBASE and three additional databases (1990–2013). Review characteristics were extracted and the methodological quality of the reviews was evaluated using the assessment of multiple systematic reviews (AMSTAR) tool. U-test, Kruskal–Wallis test, chi-square test, and multivariable linear regression analysis were used to assess the influence of review characteristics on AMSTAR-score.

Results
Fourty-six systematic reviews fulfilled the inclusion criteria. Average methodological quality was high (median AMSTAR-score: 8), but variability was large (AMSTAR range: 0–11). Quality did not differ significantly according to vaccination target group. Cochrane reviews had higher methodological quality than non-Cochrane reviews (p = 0.001). Detailed analysis showed that this was due to better study selection and data extraction, inclusion of unpublished studies, and better reporting of study characteristics (all p < 0.05). In the adjusted analysis, no other factor, including industry sponsorship or journal impact factor had an influence on AMSTAR score.

Conclusions
Systematic reviews on influenza vaccination showed large differences regarding their methodological quality. Reviews conducted by the Cochrane collaboration were of higher quality than others. When using systematic reviews to guide the development of vaccination recommendations, the methodological quality of a review in addition to its content should be considered.