It said nearly 36,000 of the volunteers have already received the second of its two-dose Covid-19 vaccine. Pfizer has as been working alongside German drugmaker BioNTech on the experimental vaccine. It contains genetic material called messenger RNA, or mRNA, which scientists hope provokes the immune system to fight the virus.
In September, Pfizer expanded the enrollment of its phase three trial to up to 44,000 volunteers from the initial target of up to 30,000. The company said the expansion would allow it to further increase diversity in the trial as well as include adolescents as young as 16 years old and people with preexisting conditions.
The phase three trials are a critical last step needed to get the vaccines cleared for distribution. Three other U.S.-backed candidates are in phase three: Moderna, AstraZeneca and Johnson & Johnson. Pfizer expects to apply for an emergency use authorization with the Food and Drug Administration next month.
In an earnings slide, Pfizer said the data monitoring board, which will assess whether the trial has been successful, has not conducted an interim efficacy analyses yet.
The update on the trial comes as Pfizer reports a mixed quarter. Third-quarter sales dropped by 4.3%, hurt in part by lower demand for some of its drugs due to the pandemic.
Sales fell to $12.13 billion, down from $12.68 billion a year earlier and lower than the $12.32 billion Wall Street analysts surveyed by Refinitiv were expecting. Still, the company's profits were slightly better than expected at 72 cents per share, higher than the 71 cents analysts were expecting.
Pfizer will hold an earnings call at 10 a.m. ET where investors will await further details on its vaccine.
Shares of the company were essentially flat in premarket trading Tuesday.