The United States on Wednesday started vaccinating children aged five to 11 against Covid-19, with roughly 28 million school-age kids now eligible for the shots that provide protection against the illness.

On Tuesday, the US Centers for Disease Control and Prevention recommended the Pfizer Inc/BioNTech SE shot for broad use in that age group after a panel of outside advisers voted in favour of it.

While about 58 percent of Americans are...