TOKYO — Postponing the 2020 Summer Olympics until next year has not erased doubts about safely hosting the world’s largest sporting event amid a global pandemic, but has merely delayed the timeline on answering them.
Japan and the International Olympic Committee announced the one-year postponement last month after enduring weeks of criticism and heavy resistance from athletes, sports federations, health experts and others.
But as the organizers of the Tokyo Games begin to confront the enormous economic, political and logistical challenges created by the unprecedented delay, it has become increasingly clear that the anxieties that forced the postponement in the first place could very well remain unsettled for many months to come.
In a hint of the hand-wringing ahead, the head of a prominent Japanese physicians’ group on Tuesday expressed doubt about whether Tokyo could hold the Olympics next year without a coronavirus vaccine.
“My personal opinion is that if an effective vaccine has not been developed, it will be difficult to hold the Olympic Games,” said Dr. Yoshitake Yokokura, the president of the Japan Medical Association. “I would not say they should not be held, but I would say that it would be exceedingly difficult.”
Research teams around the world are rushing to develop a vaccine, but most experts have said it could take 12 to 18 months to develop one, let alone distribute it globally.
Lingering uncertainty about the virus and the general safety of a huge, multinational gathering in Tokyo could mean that Olympic officials, even a year from now, would be forced to make modifications to the established elaborate model for the Games.
The officials could, among other things, decide to hold the 16-day event without a live audience and turn the Games into a strictly made-for-television spectacle. That option was already discussed in depth, and ultimately scrapped, as a possible way to avoid postponement this year.
Though such a move might appease global broadcasters, the organizers could miss out on hundreds of millions of dollars in ticket sales and have to offer refunds for those already purchased.
The cost of the Games is expected to balloon by billions of dollars because of the delay.
Indeed, any continuing safety issues will compound the logistical headache already developing for officials in Japan. Questions about securing competition venues, hotels for visitors and housing for 15,000 Olympic and Paralympic athletes from more than 200 countries, for example, remain mostly unanswered.
An I.O.C. spokesman said on Tuesday that Olympic organizers would adhere to the World Health Organization’s ongoing guidance about mass gatherings during the pandemic and move forward with the aim of holding the Games “only in a safe environment for all people involved.”
The I.O.C. and Japan have given themselves one shot to get it right. On Tuesday, Yoshiro Mori, the president of the Tokyo organizing committee, was quoted in a Japanese newspaper as saying the Games would be “scrapped” if they could not take place in the summer of 2021.
“The Olympics would be much more valuable than any Olympics in the past if we could go ahead with it after winning this battle,” Mr. Mori told the Nikkan Sports daily. “We have to believe this. Otherwise, our hard work and efforts will not be rewarded.”
As of Monday, Japan’s coronavirus death toll stood at 376, and its national caseload was over 13,000. Dr. Yokokura told reporters on Tuesday that he thought it was still too early to consider lifting the country’s state of emergency.
While the world waits for the pandemic to run its course, small moments of friction have hinted at possible complications between the I.O.C. and Japan in the year to come.
Earlier this month, some Japanese officials were irked about a Q. and A. published on the I.O.C. website that included a passage about the financial impact of postponing the Games.
The passage said Shinzo Abe, the prime minister of Japan, had agreed that his country would “continue to cover the costs it would have done under the terms of the existing agreement for 2020, and the I.O.C. will continue to be responsible for its share of the costs.”
The line, however innocuous, touched a nerve in Japan, and last week a spokesman for the Tokyo organizing committee publicly objected to the fact that Mr. Abe had been singled out by name on the website.
“Tokyo 2020 signaled us that they felt it would not be appropriate to mention the prime minister in such I.O.C. communication,” an I.O.C. spokesman said, “and we, of course, respected this wish.”
Within hours, Mr. Abe’s name was removed from the I.O.C.’s article.
Tariq Panja contributed reporting from London.