With the Tokyo Olympics just five weeks away, thousands of officials and volunteers have begun receiving their COVID-19 vaccines as organizers hope to ensure a safe Summer Games under the shadow of the coronavirus pandemic.

With just over a month until the July 23 opening ceremony, organizers are in the home stretch and are scrambling to finalize virus rules and get participants vaccinated in time.

They also face a controversial and difficult decision over how many domestic fans, if any, will be in the stands for the pandemic-postponed Games.

Japanese Olympic athletes have already begun receiving vaccines, and the rollout expanded on Friday to Olympic staff, volunteers and others who will interact with overseas participants.

The International Olympic Committee (IOC) has donated enough Pfizer/BioNTech doses for 40,000 people, including airport staff, local media and Olympic referees.

Chika Hirai, director of doping control for Tokyo 2020, was among those being vaccinated on Friday. She said she had some worrying concerns about virus risks before getting jabbed.

"Now that I will be vaccinated, I will feel a little more reassured doing my job," she told reporters.

"Many people from abroad, including inspectors from my field, are coming to Japan after having been vaccinated themselves. I feel more relieved that we also won't be the source of the virus spread."

The jabs are separate from those being used in Japan's national vaccine rollout, which began slowly but has picked up the pace lately, with over 6% of the population now fully inoculated.

The vaccinations come as organizers work to convince a skeptical public that the biggest international event since the pandemic began will be safe.

This week they have rolled out new virus rulebooks, warning athletes they could be barred from the Games if they violate regulations on mask-wearing or daily testing.

But they face a difficult decision over whether to allow spectators into the stands, with a group of leading medical experts who advise the government saying Friday a closed-door Games would be safest.

"Having no spectators would create the least risk in terms of the spread of infections inside venues, so we think this would be ideal," they wrote in a report submitted to Tokyo 2020 organizers and the government.

'Stricter standards'

The number of fans at the Games will be limited by government virus measures, which in Tokyo currently cap spectators at 5,000 people or 50% capacity, whichever is smaller.

That rule is scheduled to stay in place until July 11, even though a virus state of emergency will end on Sunday.

After July 11, the cap will be raised to 10,000 people or 50% capacity, but the experts urged Olympic organizers to "impose stricter standards" if they allow fans.

They also want limits on spectators from outside the area.

And they warned organizers should be prepared to reverse course and ban fans if the infection situation or pressure on the medical system worsens during the Games.

A final decision on local fans is expected next week, with local media reports saying a 10,000-person cap was most likely.

Overseas fans have already been barred from attending for the first time in Olympic history as organizers try to tamp down infection fears.

Tokyo 2020 said Friday they have further slashed the number of overseas participants coming to Japan for the Olympics and Paralympics to 53,000, not including around 15,500 athletes.

That is down from original plans for 177,000 people, including officials, sponsors and media, they said.

Tokyo 2020 also said Friday they had received offers from more than 100 overseas volunteer medical staff.

The foreign volunteers facilitated by the IOC are meant to help ensure the Games do not place extra pressure on Japan's medical system.