US biotech firm Moderna said Tuesday that trials had shown its Covid-19 vaccine is “highly effective” in adolescents aged 12-17 and the company would seek regulators’ approval in June.

“We are encouraged that mRNA-1273 was highly effective at preventing Covid-19 in adolescents,” CEO Stephane Bancel said in a statement.

“We will submit these results to the US FDA and regulators globally in early June and request authorization.”..

The two-dose vaccine, which is given four weeks apart, is already authorized for adults.

The phase 2/3 study the company is citing Tuesday included more than 3,700 adolescents. No cases of Covid were observed in participants who received two doses of the vaccine, while four cases were observed in the placebo group, according to the company.

No significant safety concerns have been identified, and side effects generally are consistent with those seen in an earlier trial of adults, the company said. The most common side effects after the second dose were headache, fatigue, muscle pain and chills, Moderna said.