GENEVA: The World Health Organization said COVID-19 patients should take two doses of the Pfizer and BioNTech vaccine within 21-28 days, as many countries grappled with a more highly infectious coronavirus variant.

"We deliberated and came out with the following recommendation: two 2 doses of this vaccine within 21-28 days," Alejandro Cravioto, chairman of WHO's Strategic Advisory Group of Experts on Immunization (SAGE), told an online news briefing.

He said SAGE did not recommend the Pfizer jab for travellers unless they were in a very high-risk group due to the very limited supply of anti-COVID drugs at present.

"While we acknowledge the absence of data on safety and efficacy after one dose beyond the three-four weeks studied in the clinical trials, SAGE made a provision for countries in exceptional circumstances of (Pfizer) vaccine supply constraints to delay the administration of the second dose for a few weeks to maximise the number of individuals benefiting from a first dose," Cravioto said.

He added: "I think we have to be a bit open to these types of decisions which countries have to make according to their epidemiological situations."

Kate O'Brien, a WHO immunization expert, said there was no outside limit for receiving a second vaccine dose. Alluding to delays in rolling out inoculations, she added: "Nobody expected this to be easy and we are starting to see where the road bumps are and where we need to make adjustments."