Like the US, Japan is using the Pfizer-BioNTech vaccine as part of its program. Yet Japanese regulators took two more months to approve its use.

The government says it has been deliberately cautious. After a series of vaccine scandals stretching back 50 years, Japan has one of the lowest rates of vaccine confidence in the world -- so winning over a skeptical public is crucial.

However, the decision to move slowly has been criticized by some medical professionals, including Dr. Kenji Shibuya, a professor at King's College in London, who says Japan's delayed rollout and its lack of vaccination strategy will ultimately cost lives.

Cautious approval process

Japan's approval came six weeks later, on February 14, after a smaller in-country test of 160 participants showed results consistent with the international trials. By Japanese standards that approval came quickly -- normally the process can take anywhere from one to two years. But critics say the delay cost the government valuable time.

"With a sample size of 160 people, it doesn't give you any scientific evidence on the effectiveness or safety (of a vaccine)," said Shibuya, from King's College.

Taro Kono, the minister in charge of Japan's coronavirus vaccine rollout, said the country's clinical trial was conducted to build public trust in the program.

"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," Kono said. "At the end of the day, we might have started slower, but we thought it would be more effective."

Scandal and skepticism

In the late 1980s, there was another scare with the introduction of a Japanese-produced measles, mumps and rubella (MMR) vaccine. Early versions of the vaccine were linked to aseptic meningitis, or swelling of the membranes around the brain and spinal cord. The problem was traced back to the mumps component of the MMR vaccine, which led to court action and a hefty damages payout.

The National Institute of Health Science discontinued the combined shot in 1993 and replaced it with individual vaccines.

After the MMR scandal, Shibuya says the Japanese government became "risk aware" and its national vaccination program became voluntary.

Dr. Yuho Horikoshi, an expert in infectious diseases, says the lawsuits led to a "vaccination gap," where no vaccines were approved in Japan for about 15 years.

More recently, in 2013, Japan added the human papillomavirus (HPV) vaccine to the national schedule to protect girls against the sexually transmitted virus, which is known to cause cervical cancer. However, videos of girls allegedly suffering adverse reactions started circulating on YouTube, leading the government to remove it from the national schedule.

Professor Shoji Tsuchida, a social psychology expert from Kansai University, says despite Japan's vaccine resistance there's no widespread "anti-vaxxer" movement in the country.

"Most people who don't want to take vaccination are afraid of possible side effects, and not a believer of (what they consider) 'fake' science," Tsuchida said. "Japan's past side effect cases of vaccination, especially the HPV case, is mainly affecting these people's minds."

Effort to reassure a skeptical public

Japan's resistance to vaccinations presents a problem for the government when it comes to rolling out the coronavirus vaccine.

The first Covid-19 vaccinations in Japan are being given to 3.7 million frontline health workers, with the goal of vaccinating seniors in April.

The Japanese government has asked half of the first round of doctors and nurses to keep an "observation diary," to monitor any side effects for seven weeks after receiving both doses of the vaccine.

Though the vaccine rollout is now underway, the medical community remains concerned about vaccine resistance. That has led a group of doctors, including New York-based Yuji Yamada, to launch a promotional campaign encouraging people in Japan to get the Covid-19 shots -- and they're using a cartoon dog to do it.

Outfitted in a white doctors' coat, Corowa-kun is a Shiba Inu-inspired chatbot, tasked with reassuring a skeptical public by answering questions about the vaccine. The name Corowa-kun comes from the Japanese words for "coronavirus" and "vaccine."

So far, more than 55,000 people have signed up to the app -- 70% of them women -- its creators said. According to Yamada, Japanese media initially reported on potential side effects of the vaccine. "Those might have been triggers for women who tend to think of vaccine risk more seriously and therefore women have used (the app) more," he said.

Vaccination minister Kono has thrown his support behind the app, but the government is yet to announce its own public messaging.

In the buildup to the Olympics, Shibuya says the government needs to focus on advocating to the public that the Covid-19 vaccine is safe, important and essential. He says the government must also do more to suppress the virus.

"Suppress, suppress and suppress to eliminate the community transmission -- otherwise Japan will repeat the state of emergency again and again, given a very slow vaccine rollout, said Shibuya.

"Their fundamental motivation and incentive is to revamp the economy. If they really want to hold the Olympics, they really need to suppress the transmission, so there's potentially nearly zero."