Pfizer will enroll participants as young as 12 in its large, late-stage COVID-19 vaccine trial to understand how it works in a wider age group.The US Food and Drug Administration granted permission to the drugmaker and German partner BioNTech SE to enroll the younger participants this month, according to an update on Monday on the US company's website.

The drugmaker is racing with rivals such as Johnson & Johnson, Moderna and AstraZeneca to develop a safe and effective vaccine for the coronavirus.

The companies have pledged to ensure diversity in terms of race, ethnicity, gender, age and other factors in their vaccine studies.

Pfizer last month scaled up its trial to about 44,000 participants, from up to 30,000, to enroll people as young as 16 and those with chronic, stable HIV, hepatitis C and hepatitis B.

The trial, which is being conducted in four countries including the United States, has enrolled 37,864 participants as of Monday, with 42% overall participants from ages 56 to 85.