"The vaccination process opens the debate on certification. We will discuss the suitability of a common approach to certification, as well as, if appropriate, under which circumstances certificates could be used," Michel said in the letter.

"We should touch on cooperation with third countries in relation to vaccines, which should be treated as a global public good," he added.

Michel said he would invite the European Commission to "offer a state of play on the vaccination roll-out, future production increases and the equitable access to vaccines", after which member states can share their experience on the implementation of vaccination campaigns.

"Accelerating vaccination across the EU is our absolute priority," he added.

Hungarian Prime Minister Viktor Orban said in a weekly radio interview on Friday that relying solely on COVID-19 vaccines delivered in the framework of a joint European Union order could delay the lifting of pandemic restrictions until "the end of summer or the fall". He said that adding a Chinese vaccine to Hungary's arsenal could accelerate the pace of inoculation, allowing a return to normal routines "even before summer".

Experts of Hungary's National Institute of Pharmacy and Nutrition (OGYÉI) recently conducted a Good Manufacturing Practice (GMP) inspection of the facility in Beijing where the Sinopharm COVID-19 vaccine is being produced. Department head Ferenc Lukács said on public television after the visit that the vaccine is being produced "in safe conditions, in a modern factory".

After Gergely Gulyás, the head of the Prime Minister's Office, said at a weekly press briefing on Thursday that Hungary is in advanced talks on acquiring the Chinese vaccine, European leaders started making their own inquiries, Ministry of Foreign Affairs and Trade state secretary Tamás Menczer said in a message posted on his Facebook page last weekend.