Experts have warned that the postponed date to host Tokyo Olympics and Paralympics could be unrealistic, if a vaccine for COVID-19 would not have been developed.
According to BBC sports, the Professor Devi Sridhar, a world health scientist, said the development of effective and affordable treatment would be a "game-changer" to running the games.
International Olympics Committee (IOC) coordination commission chair John Coates has also acknowledged that Covid-19 could still affect the rescheduled Olympics.
The committee rescheduled the games to take place from 23 July to 8 August 2021.
Mr. Coates said the virus could impact in terms of "mass gatherings or testing of athletes" when the time comes, adding that directions from the World Health Organizations will guide IOC.
Professor Sridhar, who is chair of global health at the University of Edinburgh, said the chances of Tokyo 2020 going ahead as planned "all depends on a vaccine".
"We're hearing from the scientists that this could be possible. I had thought it would be a year or a year and a half away but we're hearing possibly this could come sooner," said Prof. Sridhar.
"If we do get a vaccine within the next year then actually I think that Olympics is realistic. The vaccine will be the game-changer - an effective, affordable, available vaccine.
Meanwhile, Japan has declared a nationwide state of emergency until 6 May because of the country's worsening coronavirus outbreak.