WHO Director-General Tedros Adhanom Ghebreyesus called for countries around the world to join forces to tackle the coronavirus on Friday, saying that "vaccine nationalism" would only slow the response to the pandemic.
Tedros said 78 high-income countries had now joined the "COVAX" global vaccine allocation plan, bringing the total to 170 countries, adding that joining the plan guaranteed those countries access to the world's largest portfolio of vaccines.
The WHO and the GAVI vaccine alliance are leading the COVAX facility, aimed at helping buy and distribute vaccination shots fairly around the world.
But some countries that have secured their own supplies through bilateral deals, including the United States, have said they will not join COVAX.
"Vaccine nationalism will prolong the pandemic," Tedros told reporters at a WHO briefing in Geneva, without mentioning any specific countries.
Tedros thanked Germany, Japan, Norway and the European Commission for joining COVAX during the last week.
A WHO spokeswoman said earlier on Friday that the organisation does not expect widespread vaccinations against COVID-19 to be available until mid-2021, citing the need for rigorous checks on their effectiveness and safety.
The WHO's chief scientist told the briefing that no vaccine should be approved for a worldwide rollout until it had undergone sufficient scrutiny.
"No vaccine is going to be mass-deployed until regulators are confident, governments are confident, and the WHO is confident it has met the minimum standard of safety," WHO chief scientist Soumya Swaminathan said.
"These (vaccine candidates) need to go through the full Phase III trials," she said, referring to testing that usually involves thousands of participants.