The World Health Organization (WHO), in a joint statement with the COVAX initiative, called on countries opening up their borders to recognize any COVID-19 vaccine it has authorized for emergency use.

In the statement, the WHO urged "all regional, national and local government authorities" to recognize as fully vaccinated "all people who have received COVID-19 vaccines that have been deemed safe and effective by the World Health Organization."

The statement came as the European Union began rolling out its digital travel certificate that will allow vaccinated travelers to have unrestricted movement across the region. However, the EU program does not recognize the AstraZeneca vaccines manufactured in India by the country's Serum Institute — branded as Covishield—because they have not been cleared by E.U. regulators. 

Moderna, Pfizer-BioNTech, Johnson & Johnson and AstraZeneca doses manufactured in Europe by the company itself, are the only four vaccines that currently qualify under the EU certificate's criteria. 

Therefore by not recognizing those doses, the EU is effectively saying some vaccinated people don't count as being vaccinated, and is barring entry for people who live in countries that rely on COVAX for COVID-19 vaccines.

The COVAX initiative has distributed more than 89 million vaccines to 133 mainly low- and middle-income countries across Africa, Asia and Latin America.

"Any measure that only allows people protected by a subset of WHO-approved vaccines to benefit from the re-opening of travel into and with that region would effectively create a two-tier system, further widening the global vaccine divide and exacerbating the inequities we have already seen in the distribution of COVID-19 vaccines," the WHO and COVAX said in the statement. 

"Such moves are already undermining confidence in life-saving vaccines that have already been shown to be safe and effective, affecting uptake of vaccines and potentially putting billions of people at risk. At a time when the world is trying to resume trade, commerce and travel, this is counter-effective, both in spirit and outcome," the statement added.

The E.U. program would also deny entry to people who have received either of the two Chinese-manufactured vaccines made by Sinovac and Sinopharm, though there are growing questions about the effectiveness of the shots.

(With input from agencies)