Effectiveness of Influenza Vaccines in Asthma: A Systematic Review and Meta-Analysis

There is uncertainty about the effectiveness of influenza vaccination in persons with asthma and its impact on asthma outcomes, which may contribute to the suboptimal vaccination rates in persons with asthma. This systematic review and meta-analysis involved searching 12 international databases for randomized controlled trials (RCTs) and high-quality quasi-experimental and epidemiological studies (1970–2016). The risk of bias was low for 3 included RCTs. The quality of 3 included observational studies was moderate. The quality of evidence was very low for all study outcomes. Pooled vaccine effectiveness in 1825 persons with asthma from 2 test-negative design case-control studies was 45% (95% confidence interval [CI], 31%–56%) for laboratory-confirmed influenza. Pooled efficacy of live vaccines in reducing influenza was 81% (95% CI, 33%– 94%). Live vaccine reduced febrile illness by 72% (95% CI, 20%–90%). Influenza vaccine prevented 59%–78% of asthma attacks leading to emergency visits and/or hospitalizations. For persons with asthma, influenza vaccination may be effective in both reducing influenza infection and asthma attacks.