https://www.sciencedirect.com/science/article/pii/S0306987720304837?via%3Dihub
The above article talks about how young children have a smaller chance of being infected, and if they do they are more likely to shrug it off. The article posits that this is because vaccines given to children between infancy and 6 years old like varicella, Hepatitis B, MMR, Poliomyelitis, and rotavirus may interact with the COVID-19 virus and reduce virility. Vaccines for respiratory diseases especially may strengthen the lung cells and result in lower infection and mortality rates.