Researchers are making"great progress" in developing vaccines against COVID-19, with some in late-stage trials, but their first usage can't be expected until early 2021, a World Health Organization (WHO) expert said on July 22.

WHO is working to guarantee fair vaccine distribution, but in the meantime it is key to suppress the virus's spread, said Mike Ryan, head of WHO's emergencies programme, as daily new instances around the world are at near-record levels.

"We are making good progress," Ryan said, noting that several vaccines were in phase 3 trials and not one had failed, so far, in terms of security or ability to create an immune reaction.

"Realistically it's going to be the very first part of next year until we begin seeing people getting vaccinated," he told a public event on social media.

WHO was working to expand accessibility to potential vaccines and also to help scale-up production capacity, Ryan stated.

"And we need to be honest about this, since this is an international good. Vaccines for this particular outbreak are not for the wealthy, they're not for the bad, they're for everybody," he explained.

The United States authorities will pay $1.95 billion to purchase 100 million doses of a COVID-19 vaccine being developed by Pfizer Inc and German biotech BioNTech in case it proves safe and successful, the firms said.

Ryan also cautioned schools to become more careful about re-opening until neighborhood transmission of COVID-19 is in check. Debate in the United States over restarting schooling has intensified, even as the pandemic flares up in dozens of states.

"We must do all possible to bring our kids back to college, and the very best thing we could do is to stop the disease in our community," he explained. "Because if you control the disease locally, you can open the colleges."