TOKYO - Developed countries hold hundreds of millions of excess COVID-19 vaccine doses at risk of expiring before they can be given to people in developing countries that have had greater difficulty in sourcing shots, according to a recent report by Nikkei Asia.

An analysis by British research firm Airfinity revealed that around 100 million doses purchased by or promised to Group of Seven (G7) and European Union (EU) members will expire by year-end, even when taking the booster shots into account, Nikkei Asia reported on Thursday.

Meanwhile, the developed countries' around 240 million doses in total will expire within two months, at a time when it is difficult to logistically send the doses to emerging economies.

According to Airfinity, inventories in G7 and EU members will exceed 1 billion doses at the end of 2021 as supply outstrips demand.

The research company conducted the analysis assuming that all countries will administer booster shots but excluded vaccine approvals for children younger than 12.

COVID-19 vaccines supplied to advanced countries typically have shelf lives of six to seven months. Japan has purchased or agreed to buy 560 million doses. The country has fully inoculated more than 60 percent of its population, despite a slower start to its vaccination campaign than in Europe and the United States.

Shots in Japan are expected to pile up after about everyone in the country who requires inoculation will receive it by around November, according to the analysis.

According to the Cabinet Secretariat, Japan distributed Pfizer and Moderna doses to local authorities, but did not take particular note of expiration dates.