GENEVA: The COVAX vaccine-sharing scheme hopes to send millions of delayed doses of AstraZeneca's shots to Africa in June and July, but the deployment hinges on a Spanish manufacturing site securing regulatory approval, UN officials said on Friday.

Africa has been hit by a halt in vaccine exports from India which were due to make up a significant portion of the first phase of the COVAX roll-out. As a result, many recipients including health workers will not receive their second dose of the AstraZeneca shot within the recommended 12-week interval.

"The second dose gap is a huge issue," World Health Organization senior adviser Bruce Aylward told a virtual UN briefing.

"We are working hard with AstraZeneca and with our scheduling and we are about to reschedule about 16 million doses to try and cover those second doses" to be shipped out in late June and early July, he said.

COVAX aims to secure 2 billion doses for lower-income countries this year but currently faces a 200 million dose supply gap due to the India disruptions as well as delays from other manufacturers. The WHO has called for wealthier countries to advance doses to meet the shortfall.

Aylward did not elaborate on where the doses would come from. Gian Gandhi, UNICEF's COVAX coordinator, confirmed that it was seeking to provide 15-16 million doses to countries that received initial vaccine doses from India's Serum Institute.

"UNICEF is working with AZ to schedule their July deliveries to cover the shortfalls," he said in a statement to Reuters.

He added that their availability would depend on a Spanish manufacturing site receiving WHO emergency-use listing in order to produce the shot "very soon" and a rapid scale-up there. "We're hopeful that this will happen based on the indications from AZ," Gandhi added.

AstraZeneca was not immediately available for comment.