Poor countries rejected more than 100 million doses of COVID-19 vaccines in December as part of the global COVAX program, mostly because they are rapidly expiring, UNICEF spokesman said, Reuters reported.

"More than 100 million have been rejected just in December alone," Etleva Kadilli, director of Supply Division at UN agency UNICEF told lawmakers at the European Parliament.

The main reason for the rejection, she said, was the supply of doses with a short shelf life.

Poorer countries have also had to postpone deliveries because of a shortage of storage space, including a lack of refrigerators for vaccines, Kadilli said.

UNICEF data on the supply and use of delivered vaccines show that 681 million doses delivered are currently unused in about 90 of the world's poorer countries. About 30 poorer countries, including large nations such as the Democratic Republic of the Congo and Nigeria, have so far used less than half of the doses received.

According to the WHO, in January, 67% of people in richer countries were fully vaccinated, while only 8% of people in poorer countries received their first dose.