Limosilactobacillus reuteri DSM 17938 supplementation and SARS-CoV-2 specific antibody response in healthy adults: a randomized, triple-blinded, placebo-controlled trial

Background:

Studies have shown that probiotics can decrease the symptoms of respiratory tract infections as well as increase antibody responses following certain vaccinations.

Methods:

In this randomized, triple-blinded, placebo-controlled intervention study with a parallel design, 159 healthy adults without prior SARS-CoV-2infection or COVID-19 vaccination and any known risk factors for severe COVID-19 were randomly allocated into two study arms. The active treatment arm consumed a probiotic product containing a minimum of 1 × 10^8 colony-forming units of Limosilactobacillus reuteri DSM 17938 + 10 μg vitamin D3 twice daily for 6 months. The placebo arm consumed identical tablets containing only 10 μg vitamin D3. Anti-SARS-CoV-2 specific antibodies and virus neutralizing antibody titers were analyzed from blood samples collected at baseline, after 3 months, and after 6 months. Differences in serum antibody titers between the two study arms were tested with independent-test using log-transformed values.

Results:

In the intention-to-treat (ITT) analysis, SARS-CoV-2 infected individuals in the active treatment arm (n = 6) tended to have higher serum anti-spike IgG (609[168–1480] BAU/ml vs 111 [36.1–1210] BAU/ml, p = 0.080) and anti-receptor binding domain (RBD) IgG (928 [212–3449] BAU/ml vs (83.7 [22.8–2094] BAU/ml, p = 0.066) levels than individuals in the placebo arm (n = 6). Considering individuals who were fully vaccinated with mRNA-based COVID-19 vaccines, the active treatment arm (n = 10) exhibited significantly higher serum levels of anti-RBD IgA (135 [32.9–976] BAU/ml vs 61.3 [26.7–97.1] BAU/ml, p = 0.036) than the placebo arm (n = 7) >28 days post vaccination.

Conclusion:

Supplementation with specific probiotics might improve the long-term efficacy of mRNA-based COVID-19 vaccines via enhanced IgA response.