(TOKYO) — Japan launched its mass COVID-19 vaccination campaign on Wednesday, months after other major economies did so and amid concerns over whether the drive would inoculate enough people in time for the already-delayed Tokyo Olympics.

Tens of thousands of front-line health care workers will receive the first round of shots, followed by another 3.7 million in March. Then the campaign will target 36 million people aged 65 and over starting in April. The drive will later extend to people with pre-existing conditions, workers at elderly care facilities and eventually the general population, though the exact timing was unclear.

As of Wednesday, COVID-19 vaccines were being administered at only eight facilities in Japan but that was expected to expand to all 100 vaccination sites by Friday. The Japanese government has pledged to make COVID-19 vaccines free for all residents.

The rollout was delayed due to the government’s request for vaccine makers to conduct clinical trials on Japanese soil. Following a review of trial data, the Japanese Ministry of Health, Labour and Welfare announced Sunday that it has officially approved a COVID-19 vaccine developed by American pharmaceutical giant Pfizer and its German partner BioNTech — the first such vaccine authorized in the country to date.

Japan, the world’s third-largest economy, was the last member nation of the Group of Seven (G7) to give the green light for a COVID-19 vaccine. Japanese Administrative Reform Minister Taro Kono, who is in charge of COVID-19 vaccines, has defended the country’s slower approach to mass immunization.

“My take is that we need to start out very slowly, checking the system, checking if the municipality operation is OK and the reservation system is working, then speed up bit by bit,” Kono said at a press conference Tuesday evening. “We are two months after the United States. But we were three months behind in the clinical trial. So I think it is more important for the Japanese government to show the Japanese people that we have done everything possible to prove the efficacy and the safety of the vaccine to encourage the Japanese people to take the vaccine. At the end of the day, we may have started slower but we thought it would be more effective.”

Last month, the Japanese government signed a contract with Pfizer to procure 144 million doses of the two-dose vaccine, enough for 72 million. An initial shipment of around 400,000 doses from Pfizer’s factory in Belgium arrived in Japan last Friday. The Japanese government has signed contracts with the manufacturers of other COVID-19 vaccines that have yet to be authorized for use in the country, with the hope of securing enough doses for Japan’s entire population of 126 million people by mid-2021.

The lagging rollout has raised questions about whether Japan will be able to safely host the Summer Olympics in the capital as planned. Kono told reporters he’s not taking the Games into consideration with the vaccine rollout.

“My job is to deliver the vaccine,” he said. “So the Olympic Games are not in my schedule.”

The 2020 Summer Olympics were supposed to kick off in Tokyo last year on July 24. But in late March, amid mounting calls to delay or cancel the upcoming Games due to the coronavirus pandemic, the International Olympic Committee and Japanese organizers announced that the event would be held a year later. Organizers have been staunch in their determination to go forward with the Games ever since. Earlier this month, they unveiled a series of “playbooks” for how they plan to hold a safe and successful Games in Tokyo this summer amid the pandemic.

The Japanese Ministry of Health, Labour and Welfare has confirmed more than 419,000 cases of COVID-19 since the start of the pandemic, including at least 7,102 deaths. The country’s daily number of newly confirmed cases has been on the decline in recent weeks after peaking in early January. Tokyo and nine other prefectures remain under a state of emergency that was instituted to stem the virus’s spread.

Dr. Akira Kano of Fujimino Emergency Hospital in the town of Miyoshi-machi in Saitama prefecture, about 20 miles northwest of downtown Tokyo, told ABC News that his hospital has treated about 1% of Japan’s confirmed COVID-19 cases. The physician said he foresees the general population not having access to COVID-19 vaccines until August.

“It’s going to be totally impossible to reach herd immunity by the time the Olympics begins,” Kano said. “I don’t think one single person believes that can happen.”

Dr. Yohei Doi, an infectious diseases professor at Fujita Health University’s Graduate School of Medicine in Japan’s Aichi prefecture and the director of the University of Pittsburgh’s Center for Innovative Antimicrobial Therapy, told ABC News that the Japanese may be hesitant to get the COVID-19 vaccine due to widespread media coverage of adverse reactions to other vaccines.

“Historically, the relatively high incidence of aseptic meningitis that was observed following receipt of the MMR vaccine in children was highlighted by major news outlets in the 1990s and bred vaccine hesitancy,” Doi said. “More recently, non-specific symptoms that occurred among teens after receipt of the HPV vaccine were heavily reported by the media as if they were caused by vaccination.”

“It is also possible that the sense of urgency to vaccinate has not reached the levels seen in the U.S. and elsewhere, given the relatively low rates of infection in Japan so far,” he added.

A recent survey by The Asahi Shimbun, one of Japan’s largest daily newspapers, showed that 29% of people said they would “immediately” get the COVID-19 vaccine if it was free and available, while 62% would “wait and see for some time” before getting the shot. Another 8% said they did not want to get the vaccine, according to the poll.

When asked whether he thinks enough people will be vaccinated before the Tokyo Olympics, Doi replied: “That’s the million-dollar question.”

“Given the complexity of the operations, how far we’ll get by July remains highly uncertain at this point. It may ultimately come down to the interpretation of ‘ample amount of people,"” he said. “I am truly hopeful that this time there will be a change and we’ll have successful implementation of COVID-19 vaccines here.”

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