Severe COVID-19, vaccination, and mortality among individuals with asthma: A Nationwide population-based cohort study

Background: Severe coronavirus disease 2019 (COVID-19) often results in worse outcomes, including mortality, in individuals with asthma compared to those without the lung disease. However, it remains uncertain whether COVID-19 vaccination improves long-term mortality in individuals with asthma. Methods: Using the Korean National Health Insurance System database, individuals with asthma were classified into four groups based on COVID-19 vaccination and COVID-19 infection status: vaccinated/uninfected, vaccinated/infected, unvaccinated/uninfected, and unvaccinated/infected individuals. After 1:1:1:1 propensity score matching, 3384 individuals with asthma were included. The primary outcome was all-cause mortality. Two multivariable models were employed: Model 1 used the unvaccinated/infected group as the reference, while Model 2 used the unvaccinated/uninfected group as the reference. Results: Over a median follow-up duration of 350 days (interquartile ranges, 294–407 days), the mortality rate was highest in the unvaccinated/infected individuals (3481 per 10,000 person-years) and lowest in the vaccinated/uninfected individuals (94 per 10,000 person-years). In Model 1, among individuals with severe COVID-19, prior COVID-19 vaccination was associated with a 61 % reduction in mortality (hazard ratio [HR]: 0.39, 95 % confidence interval [CI]: 0.31–0.50). The risk of mortality was further decreased among uninfected individuals (HR: 0.15, 95 % CI: 0.10–0.21 for unvaccinated/uninfected individuals; HR: 0.04, 95 % CI: 0.02–0.07 for vaccinated/uninfected individuals). In Model 2, among uninfected individuals, COVID-19 vaccination exhibited a 74 % reduction in mortality risk (HR: 0.26; 95 % CI: 0.13–0.52), whereas individuals experiencing severe COVID-19 had markedly elevated mortality risks (HR: 2.69, 95 % CI: 1.84–3.92 for vaccinated/infected individuals and HR: 6.85, 95 % CI: 4.86–9.67 for unvaccinated/infected individuals). Conclusions: The COVID-19 vaccination was associated with reduced long-term mortality in individuals with asthma, regardless of COVID-19 status.