Vaccinating children aged under 5 years against covid-19

The United States has joined a handful of countries recommending that children aged 6 months to 5 years should receive covid-19 vaccines, but it is uncertain if other countries will follow. What is the evidence behind the US’s recommendation, and how does the case for vaccinating children under 5 years differ from offering covid-19 vaccines to older children? Two vaccines have been authorised for under 5s in the US, based on data supplied by manufacturers Pfizer and Moderna.