In their randomized, quadruple-blinded clinical trial including 300 symptomatic COVID-19 outpatients who started taking a probiotic mixture or a placebo mixture after testing positive for SARS-CoV-2, the probiotic group exhibited higher levels of anti-S IgG and IgM than the placebo group after 15 and 30 days.19 However, in contrast to our findings, the authors also reported significant improvements in clinical outcomes, such as symptom duration, viral load, and lung infiltrates, in the probiotic group whereas we did not observe any group-level differences in symptom duration or severity. This evidence concerns the gene CD40LG and COVID-19.