Pfizer World's headquarters are in Midtown Manhattan in New York City.
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Pfizer and German biotech company BioNTech announced on Saturday that they had submitted a proposal to the US Food and Drug Administration to expand the phase 3 study of their coronavirus vaccine to up to 44,000 participants. This is a significant increase over the previous target of 30,000.
The companies that are jointly developing the vaccine said in a statement that the study is proceeding as planned and they expect 30,000 participants to be enrolled by next week.
"The proposed expansion would enable companies to further increase the diversity of study populations and to include and provide additional safety to adolescents 16 years and older and people with chronic, stable HIV (human immunodeficiency viruses), hepatitis C or hepatitis B infections. and effectiveness data, "said the companies.
Representatives from the Food and Drug Administration and the Department of Health and Human Services did not immediately return CNBC's request for comment.
Public health professionals have emphasized that vaccine trial participants must reflect a diverse population, including the elderly, color communities, and people with underlying health conditions, all of whom are disproportionately affected by the virus. The involvement of different participants helps ensure that the vaccine candidate is truly safe and effective in a wide range of populations.
Moderna, another company developing a Covid-19 vaccine, told CNBC earlier this month that its enrollment in the study would be slowed slightly to ensure that the minorities most at risk of the disease are adequately represented.
Albert Bourla, CEO of Pfizer, said earlier this month that the drug company could get results from its late study as early as October. On Saturday, companies reiterated the possibility they might have data to show whether or not the vaccine will be effective by the end of October. However, it may take longer to collect enough data to determine whether the vaccine is safe, as months of follow-up work are required to determine what type of side effects the vaccine may cause.
"The central study is event-based and there are many variables that ultimately affect when it is read," the companies say. "As mentioned earlier, based on current infection rates, companies continue to expect a final efficacy reading by the end of October."
Through Operation Warp Speed, the Trump administration's drive to get a Covid-19 vaccine and therapeutics to market quickly, the U.S. has now invested more than $ 10 billion in six candidates, including Pfizers. The US announced in July that it had agreed to pay Pfizer and BioNTech nearly $ 2 billion for at least 100 million doses.
In July, Pfizer announced that an early clinical study showed that the vaccine produces some neutralizing antibodies that the researchers believe are necessary to build immunity to the virus.
– CNBC's Meg Tirrell contributed to this report.