Discussion
infection
VIRUS, INFECTION, EVENT, SARS-COV-2 INFECTION
The aim of this randomized, triple-blinded, placebo-controlled study was to explore whether probiotic supplementation could improve anti-SARS-CoV-2 antibody response upon infection in healthy adults. To our knowledge, this is the first study to analyze the effects of probiotic supplementation on different anti-SARS-CoV-2 antibody classes, including virus-neutralizing antibodies, throughout the whole seroconversion event.Overall, we observed a total of 15 SARS-CoV-2 infections during the study period and were able to analyze infection-induced anti-S and anti-RBD IgG levels in 12 subjects. This analysis showed a non-significant trend for higher serum anti-S (Although this study was initially designed to investigate virus-specific antibody responses following SARS-CoV-2 infection, the start of the mass vaccination campaign against COVID-19 in the spring of 2021 in Sweden provided the opportunity to analyze vaccine-induced antibody responses. Reflecting Sweden’s COVID-19 vaccination policies, most participants in our cohort were vaccinated during the intervention period with the mRNA-based COVID-19 vaccines, BNT162b2 and mRNA-1273, which lead to the production of IgA and IgG against the spike antigens (S and RBD) of SARS-CoV-2.In our initial statistical analysis, we did not observe any differences in vaccine-induced anti-S and anti-RBD IgG or IgA responses in fully vaccinated individuals between the study arms. Also, we did not measure any group-level differences in SARS-CoV-2 nAB titers after full vaccination. It is important to note that although the virus-specific IgG and IgA levels correlated positively with the measured nAB titers (Supplementary Information), virus neutralization was determined against the B.1.617.2 (Delta) variant that has shown reduced sensitivity to vaccine generated antibodies.To the best of our knowledge this the first study to investigate the effects of probiotic supplementation on anti-SARS-CoV-2 antibody response, including virus-neutralizing antibody titers, in exclusively SARS-CoV-2 antigen-naïve individuals. Nevertheless, this study has several strengths and limitations that should be considered when interpreting the results. Regarding the strengths, in the previously mentioned studies, the intervention period commenced after a positive test resultIn conclusion, supplementation with a probiotic strain 