TOKYO: Japan began vaccinating healthcare workers against the coronavirus on Wednesday, as it rolled out a cautious inoculation programme with just over five months until the Tokyo 2020 Olympics.

Japan has so far approved only the Pfizer/BioNTech vaccine, and started administering the first shots at a Tokyo hospital on Wednesday morning.

Tokyo Medical Centre director Kazuhiro Araki volunteered to be the first at the facility to receive the shot.

"The vaccine plays an important role in anti-coronavirus measures. So I thought as a director I should take the lead and get the shot," he told reporters afterwards.

"I don't like getting shots very much," he admitted.

"But it wasn't painful, so it was good. I was relieved."

Nurse Rino Yoshida, wearing a face mask and visor, was calm and relaxed as she too became one of the first people in Japan to be vaccinated outside of clinical trials.

"I felt it going in but it wasn't sore. There's no real pain or swelling," she told national broadcaster NHK."The mortality rate and the risk of illness have gone down overseas, so hopefully vaccinations starting in Japan can change the situation here," she said.

Twelve staff at the facility are being vaccinated on Wednesday, in front of the media, with a total of 800 in line to receive shots, including administrative personnel.

Japan is planning to initially vaccinate 40,000 healthcare workers across the country, and will study the effects of the two-dose vaccine on 20,000 of them.

Doses will be administered three weeks apart, with the people in the study group asked to keep daily records of any side effects or reactions, local media said.

The country then hopes to vaccinate around 3.7 million health workers from March -- with jabs for around 36 million people aged 65 or older starting from April.

The programme will extend later to those with preexisting conditions or working with the elderly, and eventually to the general population, but there has been little detail yet on the timing for that.