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–Guérin (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 PV1 (vaccine against poliomyelitis) 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
Citation: The Pharmaceutical Journal DOI: 10.1211/PJ.2020.20207845