There were no COVID-19 diagnoses in those given two doses of the Moderna vaccine compared with four cases among kids given dummy shots. In a press release, the company also said the vaccine appeared 93% effective two weeks after the first dose.

While children are far less likely than adults to get seriously ill from COVID-19, they represent about 14% of the nation’s coronavirus cases. At least 316 have died in the U.S. alone, according to a tally by the American Academy of Pediatrics.

With plenty of vaccine supply in the U.S., younger teens flocked to get Pfizer’s shot in the days after FDA opened it to them, part of a push to get as many kids vaccinated as possible before the next school year.

Both Pfizer and Moderna have begun testing in even younger children, from age 11 down to 6-month-old babies. This testing is more complex: Teens receive the same dose as adults, but researchers are testing smaller doses in younger children. Experts hope to see some results in the fall.