GENEVA, Switzerland (AFP) — Experts at the World Health Organization (WHO) gave cautious backing on Tuesday to a move already taken by some countries to delay giving out the second jabs of the Pfizer-BioNTech coronavirus vaccine.

Faced with limited supplies of the vaccines, Denmark and Britain have both said they would wait for longer than the recommended 21-28 days between jabs so they could focus on giving more people their first dose.

The WHO’s vaccine advisory group said the jabs could be administered a few weeks beyond the recommended 21-28 days in exceptional circumstances.

However, there is no data confirming the safety and efficacy of doing so.

The WHO granted emergency validation to the Pfizer-BioNTech vaccine last Thursday, paving the way for countries worldwide to give swift approval to its import and distribution.

The vaccine was the first to receive the WHO’s nod since the novel coronavirus broke out in China a year ago.

The jab is administered in two doses — but the WHO’s Strategic Advisory Group of Experts on Immunisation (SAGE) said on Tuesday that the second one could be delayed, in order to allow more people to benefit from the first.

“SAGE recommends the administration of two doses of this vaccine within 21 to 28 days,” the group’s chair Alejandro Cravioto told a virtual news conference.

But he added that “countries in exceptional circumstances of vaccine supply constraints and epidemiologic settings” could delay the administration of the second dose.

Kate O’Brien, director of the WHO’s immunisation department, said the delay should not exceed six weeks, based on the “outer limit” of clinical trials.