About 740,000 COVID-19 booster vaccine doses made by Moderna have been discarded or are expected to be discarded in 27 major cities in Japan due to expiration, a Kyodo News survey showed Saturday, as the country struggles to expand the number of people getting third shots.

The survey, conducted from May 17 to Thursday, asked 52 major cities whether they have scrapped or plan to scrap government-provided Moderna booster doses, many of which have an expiration date between April and June.

Such doses amounted to 739,085 shots in total, with the volume of wasted doses per municipality varying from 645 to 120,000. The Moderna-made vaccine expires in nine months compared with Pfizer's 12 months.

The survey results also reflect the younger population's apparent reluctance to receive a third shot and more people preferring Pfizer shots as adverse reactions such as pain and fever are more frequently reported with Moderna shots.

Government-supplied Moderna boosters are used across the country, and not limited to the 52 cities, so similar cases could be found elsewhere.

About 75 million people had received booster shots by Friday, according to the government. Of those, about 31 million were administered the Moderna vaccine, while about 44 million were given Pfizer vaccine.