BACKGROUND: Milder symptoms were observed in children with COVID-19. However, whether this also holds true for neonates is not known. METHODS: The clinical data of a total of 3213 patients aged 2 years or below, including 749 neonates, in Brazil nationwide were studied. Comparisons were made between neonate and infant patients by conducting statistical tests. RESULTS: Neonates appeared to bear more severe clinical courses. In addition to higher case fatality rates, newborns with COVID-19 had much shorter time from symptom onset to death and longer time from symptom onset to discharge. Dyspnoea, sore throat and cough were more prominent in neonate patients, suggestive of both upper and lower respiratory tract infection, as opposed to upper respiratory tract symptoms mostly observed in children. CONCLUSION: Findings suggested that trained immunity provides a possible explanation because the innate immune system in newborns is not "well-trained" while that in adult tends to hyperactive.