Data published earlier in 2020 suggest that children are at lower risk of experiencing severe symptoms and mortality from COVID-19, as well as suggesting that risk seems to increase with age
I have a hypothesis that could explain this: children are being protected by the childhood vaccination programme.
Looking at China’s vaccination programme, at birth, infants receive two vaccines: the Bacillus Calmette–GuÃ©rin (BCG) vaccine, which protects primarily against tuberculosis, and the hepatitis B vaccine.
BCG usually protects individuals for around 20 years, while the hepatitis B vaccine (which is administered in three doses: at birth, at one month and at six months) gives protection for around 10 years
. Perhaps other childhood vaccines, such as the inactivated poliovirus vaccine, offer this protection against the COVID-19.
With the current lack of vaccination against COVID-19, perhaps people aged over 20 years should be vaccinated with the hepatitis B vaccine. This age could be increased to 50 years, if that approach is not cost effective.
Souad Moumene, practice pharmacist, Manchester
 Centers for Disease Control and Prevention. 2020. Available at: https://www.cdc.gov/mmwr/volumes/69/wr/mm6912e2.htm?s_cid=mm6912e2_w (accessed March 2020)