Risk factors of severe influenza A H1N1: a Meta-analysis

Abstract

Objective To explore the risk factors of severe influenza A H1N1 by the Meta-analysis so as to provide a reference for prevention and control. Methods Literatures on risk factors of severe influenza A H1N1 were retrieved in Chinese Biomedical Medicine, China national knowledge internet (CNKI), Wanfang Database, VIP Database, PubMed and ProQuest from 1st January 2000 to 31st December 2018 by computer. Quality of literatures were evaluated with the Newcastle-Ottawa Scale (NOS) on standard quality evaluation. Heterogeneity test of literatures was analyzed with the RevMan 5.1, and the odds ratio (OR) and 95% confidence interval (CI) was calculated with the Meta-analysis. Results A total of 10 literatures were included. Among those literatures, there were 1 852 cases in case group, 3 049 cases in control group and 8 risk factors. Meta-analysis showed that the risk factors of severe influenza A H1N1 included ages ≤5 years (OR=6.09, 95%CI: 1.77-21.16) , pregnancy (OR=11.80, 95%CI: 6.91-20.16) , chronic underlying disease (OR=3.74, 95%CI: 2.34-5.97) , BMI≥30 kg/m2 (OR=4.48, 95%CI: 2.81-7.12) , time between attack and seeking medical advice≥48 h (OR=1.85, 95%CI: 1.50-2.28) and infected with HIV (OR=1.74, 95%CI: 1.33-2.27) with statistical differences (P<0.001) . Influenza vaccination which was a protective factor had a negative influence on incidence of severe influenza A H1N1 (OR=0.63, 95%CI: 0.49-0.82) . Conclusions Risk factors of severe influenza A H1N1 comprise ages≤5 years, pregnancy, chronic underlying disease, BMI≥30 kg/m2, time between attack and seeking medical advice≥48 h and infected with HIV, and influenza vaccination is a protective factor. Influenza vaccination can effectively reduce the incidence of severe influenza A H1N1 or slow down the disease progression. Evidence on gender as a risk factor of severe influenza A H1N1 is insufficient which needs to be tested by later researches. Key words: Influenza A virus, H1N1 subtype; Risk factors; Meta-analysis