Japan on Sunday formally approved its first COVID-19 vaccine and said it would start nationwide inoculations within days, but months behind the US and many other countries.

Japan's health ministry said it had approved the vaccine co-developed and supplied by Pfizer Inc.The announcement comes after a government panel on Friday confirmed that final results of clinical testing done in Japan showed that the vaccine had an efficacy similar to what overseas tests showed.

Many countries began vaccinating their citizens late last year, and Pfizer's vaccine has been used elsewhere since December.

Under the current plan, about 20,000 front-line medical workers at hospitals in Japan will get their first shots beginning around Wednesday. About 3.7 million other medical workers will be next, followed by elderly people, who are expected to get their shots in April. By June, it's expected that all others will be eligible.

Vaccines are considered key to holding the delayed Tokyo Olympics this summer. Japan is expected to receive 144 million doses from Pfizer, 120 million from AstraZeneca and about 50 million from Moderna before the end of this year, enough to cover its population.

Vaccines being developed by Japan are still in the early stages, so the country must rely on imports. AstraZeneca applied for approval in Japan only recently, while Moderna hasn't applied yet. Japan's reliance on the imports, many of them subject to EU export controls, is also causing concerns about supplies.