Pfizer Inc and BioNTech have proposed to the US Food and Drug Administration (FDA) to expand their Phase 3 pivotal Covid-19 vaccine trial to about 44,000 participants while increasing the diversity of the trial population.

The initial target figure for the trial was up to 30,000 participants, which the companies said they expect to reach by next week.

The proposed expansion would also allow the companies to enroll people as young as 16 and people with chronic, stable HIV, hepatitis C and hepatitis B, they added.