Japan's Takeda Pharmaceutical Co. said Tuesday it will import an additional 50 million doses of U.S. developer Moderna Inc.'s coronavirus vaccine from as early as the beginning of 2022, in a move that could help speed up inoculation efforts in the country.

The additional doses, to be provided based on a three-way agreement with Moderna and the Ministry of Health, Labor and Welfare, will bring the total number of doses of the vaccine to 100 million. Takeda handles the sale and distribution of the vaccine in Japan.

Takeda said the agreement "includes the potential to secure and supply vaccines corresponding to COVID-19 variants or booster products, should they be successfully developed by Moderna" and licensed by the ministry.

It is not yet known how long the effect of the COVID-19 vaccine will last. Other countries have begun administering booster shots, or third or subsequent doses, to prolong immunity.

In response to the agreement, health minister Norihisa Tamura told reporters, "We will continue to work together to ensure a smooth supply of vaccines."

The central government has already signed an agreement to receive 50 million doses of Moderna's vaccine by the end of 2021. The vaccine is being used in mass vaccination sites and workplace inoculations in Japan, but the government has said supplies are limited.

Discussions are also underway between the health ministry and Takeda to secure 150 million doses of the vaccine developed by U.S. pharmaceutical giant Novavax Inc. starting in early 2022.