Johnson & Johnson plans to start testing its experimental COVID-19 vaccine in youths aged 12 to 18 as soon as possible, a company executive said at a meeting held by the US Centers for Disease Control and Prevention (CDC) on Friday.

“We plan to go into children as soon as we possibly can, but very carefully in terms of safety,” J&J’s Jerry Sadoff told a virtual meeting of the U.S. Centers for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices on Friday.

Depending on safety and other factors, the company plans to test in even younger children afterwards, said Sadoff, a vaccine research scientist at J&J’s Janssen unit, without giving a timeline.

The Centre today began preparations for the introduction of potential Covid-19 vaccines, asking states to create three-tier mechanism to facilitate the process. In a letter to chief secretaries, Union Health Secretary Rajesh Bhushan said Covid-19 vaccine introduction would most likely span over a year with multiple groups being included sequentially starting from healthcare workers.

He said the vaccine would initially be available in limited quantities. “It is anticipated that initially the supply of vaccine will be limited in view of huge demand, hence prioritisation of socio-demographic groups will be done for vaccination and subsequently other groups will be included,” states the Health Secretary’s letter.