Meta-analysis of whether influenza vaccination attenuates symptom severity in vaccinated influenza patients.

Background: Influenza vaccination has been associated with decreased risk of influenza-related infections. However, associations between influenza vaccination and the severity of influenza cases have not been systematically summarized. We conducted a meta-analysis to evaluate whether influenza vaccination could attenuate symptom severity in vaccinated influenza patients.

Methods: A systematic literature search was performed using the PubMed, Web of Science, EMBASE, and Scopus databases. A quantitative synthesis of the data was conducted using a fixed/random effects model in the meta-analysis.

Results: A total of seven studies, involving 6342 vaccinated and 7036 non-vaccinated patients were included. Compared with non-vaccinated, vaccinated patients were significantly less likely to develop a fever (OR = 0.66, 95% CI: 0.43-0.89), be admitted to the ICU (OR = 0.79, 95% CI: 0.64-0.97), suffer mortality (OR = 0.55, 95% CI: 0.34-0.89), stay in the ICU (WMD = -1.37, 95% CI: -2.15 to -0.60) or stay in the hospital (WMD = -0.32, 95% CI: -0.61 to -0.04).

Conclusion: Those benefits that could be highlighted in the communication material to enhance the uptake of influenza vaccination among both the public health nurses and the community as a whole.