LONDON - The Pfizer/Biontech Covid vaccine is safe and 100 per cent effective in children as young as 12, the company has announced.

The two pharmaceutical giants carried out trials of the vaccine on 2,260 children aged between 12 and 15 in the US.

Preliminary data showed there were no cases of coronavirus among fully vaccinated adolescents compared to 18 children who were given a placebo.

Those given a placebo in the trial became infected with Covid-19 while none in the vaccinated group did, the companies said.  Side effects in adolescents were consistent with those observed in participants 16 to 25 years old.

Pfizer shares dipped 1.4 per cent to $36.11 despite the announcement, while shares in Germany-based Biontech surged 8.9 per cent to $104.44.

A spokesperson said Pfizer and Biontech will ask the US regulator to approve emergency authorisation of the jab on school pupils next week, in a bid to inaugurate its wide scale rollout when the new academic year starts in the autumn.

Currently, the Pfizer jab is only available to over-16s in both the US and the UK.

“We share the urgency to expand the use of our vaccine,” Pfizer chief executive Albert Bourla said in a statement.

Experts have said that vaccinating children of all ages will prove crucial to slowing the spread of the pandemic.

Last week, Pfizer and Biontech began testing their vaccine in children aged between 5 to 11, while the firms are set to begin testing in ages 2 to 5 from next week. Results from those trials should be available later this year.