Effect of probiotics on humoral responses to COVID-19 vaccination in older adults: a randomized, placebo-controlled trial (PIRATES-COV study).
Gut MicrobesJul 28, 2026 (epub)
Jean-Charles Pasquier, Nils Chaillet, Mélanie Plourde et al.
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In 30 seconds
This randomized controlled trial evaluated the effect of probiotics on immune responses to COVID-19 vaccination in older adults (ages 65-89) in Quebec, Canada. The study found no significant difference in the proportion of participants without detectable anti-S1-RBD antibodies at 6 months post-vaccination between the probiotic and placebo groups (1.2% vs 1.6%).
Key findings
- At 6 months post-vaccination, 1.2% of the placebo group and 1.6% of the probiotic group had undetectable anti-S1-RBD antibodies.
- Anti-N seropositivity was lower in the probiotic group at 6 months, with an odds ratio of 0.6 (95% CI 0.4-0.9; p = 0.02).
- Self-reported COVID-19 infection incidence was 16.5% overall, with 19.1% in the placebo group and 13.9% in the probiotic group.
Why it matters
Understanding the role of probiotics in enhancing immune responses to COVID-19 vaccination in older adults is crucial, given their high risk for severe disease. This study provides insights into potential adjunctive therapies to improve vaccination outcomes in this vulnerable population.