Which coronavirus vaccine candidate is the one to closely monitor right now? There's a good case to be made that it's BNT162b2, which was developed by Pfizer (PFE 1.80%) and BioNTech (BNTX -0.40%).

A lot of action should happen between now and the end of the year for BNT162b2. Here are three critical near-term milestones to watch with Pfizer's coronavirus vaccine.

Syringe with needle on top of a calendar.

Image source: Getty Images.

1. Preliminary phase 3 results (potentially by late October)

Pfizer and BioNTech began a global phase 2/3 study of BNT162b2 on July 27, 2020. At that time, the two companies indicated that they could seek regulatory review as early as October 2020. However, Pfizer CEO Albert Bourla stated in an open letter last week that the timeline has changed.

Bourla also said that Pfizer "may know whether or not our vaccine is effective by the end of October." A specified threshold of COVID-19 cases needs to occur in individuals who received a placebo. When that threshold is reached, Pfizer and BioNTech will be able to see if their coronavirus vaccine provided statistically significant protection against infection by SARS-CoV-2, the virus that causes COVID-19.

An independent committee will make this determination since both Pfizer and BioNTech are blind as to which study participants received BNT162b2 and which ones received a placebo. When Pfizer knows the results, though, the world will know them soon afterward. Bourla said that "in the spirit of candor, we will share any conclusive readout (positive or negative) with the public as soon as is practical, usually a few days after the independent scientists notify us."

2. EUA submission (by the third week of November)

Bourla expects that Pfizer will file for emergency use authorization with the U.S. Food and Drug Administration by the third week of November. Why did the big drugmaker push back its timeline for EUA submission? The FDA issued guidelines that Pfizer didn't know about until recently.

Earlier this month, the FDA released guidelines regarding its EUA process for coronavirus vaccine candidates. The most important requirement is that drugmakers must provide two months of safety data for at least half of the participants in a late-stage clinical study following the vaccine's final dose.

BNT162b2 requires two doses. Pfizer's countdown to EUA filing began when half of the roughly 44,000 participants in its late-stage study received the second dose of the vaccine. 

3. FDA EUA decision (potentially by late December)

It's unclear how long it will take the FDA to decide on any EUA filings. The agency plans to convene an advisory committee of outside infectious disease experts to review all EUA submissions. The committee will recommend whether or not the FDA should grant EUA based on the regulatory submission data.

Perhaps the best guess is that the FDA will decide on Pfizer's EUA filing by late December, assuming Pfizer submits its EUA filing in late November. It will probably schedule an advisory committee meeting soon after this submission. The FDA will probably make its final decision within a week or two after receiving the committee's recommendation. Remember, these are only conjectures as to how quickly the agency will move forward.

The FDA is under a lot of pressure from two directions. It doesn't want to be accused of rushing the process at the expense of Americans' safety. On the other hand, the agency also wants to grant EUA for a coronavirus vaccine as soon as possible. 

Falling dominoes

The stakes of achieving these milestones are high for Pfizer and BioNTech. If BNT162b2 wins EUA, the two companies stand to receive $1.95 billion to supply 100 million doses to the U.S. government. That deal could be expanded to include another 500 million doses. 

Investors should view these three critical milestones like dominoes. If the first domino doesn't fall, none of them will. Pfizer seems to be in a pretty good position to achieve all three milestones within the next three months, but if the company doesn't, it will be the big pharmaceutical stock that falls.