A statement from Pfizer (NYSE:PFE) released Friday suggests the company's coronavirus vaccine candidate could be ready for distribution throughout the U.S. by the end of November. In the open letter, CEO Albert Bourla laid out the three hurdles the company's coronavirus vaccine candidate needs to clear before the FDA will consider granting an emergency use authorization (EUA) for it.

The first hurdle, proof of efficacy, can't be evaluated until a certain number of clinical trial volunteers test positive for COVID-19 after being inoculated with the vaccine candidate, dubbed BNT162, or a placebo. Since the pandemic has continued to spread largely unchecked across the U.S. since the beginning of Pfizer's phase 3 trial, the number of events required to trigger an interim analysis should cross the minimum threshold soon. Over the past three weeks alone, over 1 million Americans have tested positive for COVID-19.

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The second hurdle is the ability to supply two months of safety data taken from at least half of the participants in the phase 3 study supporting the EUA request. While the timing is by nature fuzzy when it comes to efficacy data, Bourla was able to confidently state that the BNT162 program will approach the FDA's safety data requirement in the third week of November. This timeline is firm because we know that by Sept. 14, Pfizer and its vaccine collaboration partner, BioNTech (NASDAQ:BNTX), had already enrolled 29,012 people in the study, which is expected to have a total of around 44,000 participants.

The first two hurdles are the hardest to cross, but it's the third that can trip up a fast-moving drug development program and bring it crashing to a halt just steps away from the finish line: Pfizer and BioNTech will need to show the FDA proof that their manufacturing process can produce BNT162 at scale while consistently meeting quality and safety standards.

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