The Japanese government is considering asking Pfizer Inc. to speed up its delivery of COVID-19 vaccine beyond the fall amid concern about a supply shortage, a government source said Thursday.

Prime Minister Yoshihide Suga is expected to make the request in an upcoming meeting with the U.S. pharmaceutical giant's CEO, Albert Bourla, the source said.

Photo shows vials of Pfizer Inc.'s COVID-19 vaccine. (Kyodo)

Under existing agreements with Pfizer, Japan will receive 100 million vaccine doses by June, 70 million between July and September, and another 20 million in or after October.

According to the source, the government wants the last batch of 20 million doses earlier in order to ease concern among local authorities that have been forced to halt reservations to administer shots to residents after Taro Kono, the minister in charge of vaccination efforts, warned that demand was beginning to outstrip supply.

In April, Suga successfully asked Bourla by phone to increase the amount of Pfizer vaccine being provided to Japan. The request led to an agreement for an additional 50 million doses.

About 23 percent of Japan's population has been fully inoculated against COVID-19 as of Tuesday, with about 35 percent having received at least one shot.

The government is reluctant to call for more supply than already agreed upon, as many poorer countries are much further behind in their vaccination efforts.

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