Researchers say between 70% and 85% of a population would need to be protected through infection or vaccination to achieve herd immunity, the point when so many people are immune that the virus has nowhere to go and even those who aren’t immune have protection.

“It’s hard to do that just in terms of numbers if you’re not going to vaccinate kids,” said Adam Ratner, chief of pediatric infectious diseases at Hassenfeld Children’s Hospital in New York.

Children and adolescents make up 22% of the U.S. population, according to the Census Bureau’s latest projections, and 18% of the population of the European Union…

Moderna is aiming to have its vaccine available for adolescents before the start of the 2021 school year and recently launched another trial with children as young as six months.