Pfizer Inc and BioNTech SE on Saturday 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.
Drugmakers racing to develop a safe and effective coronavirus vaccine pledged in July to ensure their larger clinical trials would include diverse sets of volunteers.
"Diversity in clinical trials is a priority for Pfizer and is critical given that Covid-19 disproportionately impacts communities of color in the US ," Pfizer's Chief Business Officer John Young said in a US congressional hearing in July.
If the study is successful, the companies could submit the vaccine for regulatory approval as early as October, putting them on track to supply up to 100 million doses by the end of 2020 and 1.3 billion by the end of 2021.
"As stated previously, based on current infection rates, the companies continue to expect that a conclusive readout on efficacy is likely by the end of October," the companies added in the joint statement on Saturday.
The vaccine candidate utilizes chemical messenger RNA to mimic the surface of the coronavirus and teach the immune system to recognize and neutralize it. Although the technology has been around for years, there has never been an approved messenger RNA (mRNA)vaccine.