Seasonal influenza is a significant health issue in the world, particularly to people with respiratory conditions, which are chronic like asthma and COPD. Although vaccine use in the high-risk groups is widely advised, influenza vaccination efficacy varies with age, type of vaccine, strains circulating and aspects of pandemics. The systematic review and meta-analysis summarize the evidence of influenza vaccine effectiveness among populations with respiratory diseases in the prevention of infections, severe outcomes, and safety. A systematic literature search was performed in various databases, such as PubMed, Embase, and Cochrane studies published between 2015 and 2025, in line with PRISMA 2020. Searches were restricted to randomized controlled trials, cohort, and case-control studies that provided quantitative measures of vaccine effectiveness against laboratory-confirmed influenza, hospitalization, or exacerbations in the asthmatic population, COPD, or other respiratory diseases. The ROBINS-I tool was used in data extraction and quality assessment. Meta-analyses used fixed- and random-effects models, heterogeneity measured using I 2 and Cochrans Q. Subgroup analysis covered age groups, vaccine preparations, outcome measures, and time. The funnel plots and statistical tests were used to assess publication bias. A total of fifteen studies showed a combined vaccine protection of about 32-35% against influenza infection, with greater efficacy among children (>40%) and less among the older ones (18%). Vaccine Effectiveness (VE) had a greater resistance to hospitalization (38%) compared to outpatient visits (~14%). There were differences on the vaccine type, circulating strains and year of pandemic. It was not possible to detect any significant rise in adverse respiratory events after vaccination. There was a high heterogeneity of studies but directionality was towards vaccination. Immunization against influenza offers moderate but significant protection in the population with respiratory illnesses, underlining the importance of influenza vaccination as one of the primary preventive measures. More refined formulations and more customized strategies can be beneficial to enhance the results and continue to vaccinate vulnerable populations.
Moazzam et al. (Sun,) studied this question.