In the original Moderna Covid-19 vaccine clinical trials for infants aged 6-23 months, Moderna reported that 9 children who received the vaccine experienced "serious adverse events within 28 days of any injection," 5 of whom were hospitalized. In contrast, no child who received the placebo had a serious adverse event or was hospitalized, although this group was one-third the size of the vaccine group. Given the small size of the study (2,350 infants), Moderna correctly notes that "these imbalances" between the vaccinated and placebo groups may have "occurred by chance." On the other hand, they may have occurred because the mRNA vaccine compromised their immune systems, an effect reported by a 2022 paper in the journal Food and Chemical Toxicology. Without a clinical trial with many more children than this study involved, there is no way to be certain.