"Introduction
... COVID-19 is more likely to affect older patients with comorbidities, as only 889 of 72,314 (1.2%) such adult cases were asymptomatic cases. In contrast, 12.9% of pediatric cases have been asymptomatic cases.
It has remained unclear as to why the infection rate of COVID-19 in children has been less than that in adults. One possible reason is that children have less exposure and more protection by their guardians; another possibility is that children have more active innate immune responses. Most infants have received regular immunizations in China and other Asian countries, including Bacillus Calmette Guerin (BCG), which has been demonstrated to provide non–specific protection against influenza infections, possibly via the induction of trained innate immunity. However, the underlying features of such BCG-mediated protection and the association of BCG vaccinations and clinical manifestations in children with COVID-19 have remained largely unknown. Therefore, in the present study, we explored the associations of BCG vaccination and clinical manifestations in pediatric patients with COVID-19...
Methods
Patient and data selection: All pediatric patients with COVID-19 were recruited from two hospitals during the specific period from January 28 to March 12, including 240 laboratory—confirmed cases from Wuhan Children’s Hospital, 56 suspected cases and 8 imported confirmed cases from Shanghai Children’s Medical Center...
Discussion
... In the present study, we found that pediatric patients with BCG vaccinations exhibited clinical features similar to those of patients who did not receive BCG vaccinations. Furthermore, the percentage of asymptomatic patients was positively correlated with age, suggesting that the severity of pediatric patients was related to the maturity of immune function...
In the present study, we found that the percentage of asymptomatic COVID-19 infections increased with age, whereas the percentage of symptomatic COVID-19 infections decreased with age. It suggests that immune function gradually matures with age, and the more vigorous immune response mounted by adults may also explain the detrimental immune response associated with acute respiratory distress syndrome...
Conclusions
In conclusion, pediatric COVID-19 patients with BCG vaccinations exhibit clinical manifestations similar to those of patients who had not been vaccinated for BCG, and the severity of symptoms in pediatric patients may be related to the maturity of immune function."
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