Moderna has said its Covid-19 vaccine strongly protects kids as young as 12, a step that could put the shot on track to become the second option for that age group in the United States.

The company studied more than 3,700 12- to 17-year-olds. Preliminary findings showed the vaccine triggered the same signs of immune protection in kids as it does in adults, and the same kind of temporary side effects such as sore arms, headache and fatigue, according to an AP report.

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 per cent effective two weeks after the first dose.