Proton pump inhibitors (PPIs) may increase the risk of COVID-19 among non-vaccinated subjects via various mechanisms, including gut dysbiosis. We aimed to investigate whether PPIs also affect the clinical outcomes of COVID-19 among vaccine recipients.
This was a territory-wide cohort study of 3 272 286 vaccine recipients (aged ≥ 18 years) of ≥ 2 doses of either BNT162b2 or CoronaVac. Exclusion criteria included prior gastrointestinal surgery, immunocompromised status, and prior COVID-19. The primary outcome was COVID-19, and secondary outcomes included COVID-19-related hospitalization and severe infection (composite of intensive care unit admission, ventilatory support, and/or death). Covariates include age, sex, the Charlson Comorbidity Index, comorbidities, and concomitant medication use. Subjects were followed from index date (first dose of vaccination) until outcome occurrence, death, additional dose of vaccination, or March 31, 2022. Exposure was pre-vaccination PPI use (any prescription within 90 days before the index date). Propensity score (PS) matching and a Poisson regression model were used to estimate the adjusted incidence rate ratio (aIRR) of outcomes with PPI use.
Among 439 154 PS-matched two-dose vaccine recipients (mean age: 65.3 years; male: 45.7%) with a median follow-up of 6.8 months (interquartile range: 2.6-7.9), PPI exposure was associated with a higher risk of COVID-19 (aIRR: 1.08; 95% confidence interval [95% CI]: 1.05-1.10), hospitalization (aIRR: 1.20; 95% CI: 1.08-1.33), and severe infection (aIRR: 1.57; 95% CI: 1.24-1.98). Among 188 360 PS-matched three-dose vaccine recipients (mean age: 62.5 years; male: 49.0%; median follow-up: 9.1 months [interquartile range: 8.0-10.9]), PPIs were associated with higher infection risk (aIRR: 1.11; 95% CI: 1.08-1.15) but not other outcomes.
Although PPI use was associated with a higher COVID-19 risk, severe infection was limited to two-dose but not three-dose vaccine recipients.

© 2024 The Authors. Journal of Gastroenterology and Hepatology published by Journal of Gastroenterology and Hepatology Foundation and John Wiley & Sons Australia, Ltd.