Japan will shorten the interval for COVID-19 booster shots for senior citizens in general from eight months to seven from February next year, Prime Minister Fumio Kishida said Friday, as the country ramps up efforts to curb the spread of the Omicron coronavirus variant.

An eight-month interval has been set "in principle" between the second and third vaccination shots, but the government is seeking to prioritize boosters for the elderly and health care workers.

Kishida also told reporters that Japan has reached a basic agreement with Pfizer Inc. to secure 2 million doses of the U.S. pharmaceutical giant's orally administered drug for COVID-19. The oral COVID drug is regarded as vital by Japan to fighting the pandemic.

Prime Minister Fumio Kishida speaks to reporters at the premier's office in Tokyo on Dec. 17, 2021. (Kyodo)

The interval for administering the booster shots for health workers and those at high risk of infection, such as the elderly at nursing homes will be reduced to six months, he added.

Japan started earlier this month administering the third doses of the vaccine developed by Pfizer Inc. and BioNTech SE to health care professionals inoculated with their second dose at least eight months ago.

Currently, the health ministry has given the green light for the vaccines of Pfizer vaccine and U.S. biotechnology firm Moderna Inc. to be used in booster shots. The ministry's fast-track approval was given to Moderna's vaccine as booster shots on Thursday.

Earlier Friday, Kishida spoke by phone with Albert Bourla, chief executive of Pfizer, and asked the U.S. pharmaceutical company to bring forward Japan's contracted supply of coronavirus vaccine, a government official said.

According to the government's announcement in November, it plans to supply 24 million doses of Pfizer vaccine and 17 million doses of Moderna's vaccine to local governments by February.