On Tuesday, BioNTech (BNTX -2.07%) confirmed what its big pharma partner, Pfizer (PFE 0.66%), had already let out of the bag: The companies hope to have phase 3 results for their coronavirus vaccine candidate by October.

In late July, the duo selected the best vaccine from its early candidates to take into phase 2b/3 development and started the study shortly thereafter. Once the clinical trial is fully enrolled and all of the approximately 30,000 subjects have received the vaccine and placebo, it'll take another 21 days before the subjects will get their booster shots.

Assuming the drugmakers wrap up enrollment in the next week or so, the last booster for the final patient would be given in the middle of September. That doesn't give much time before the self-imposed expectations for data in October.

Gloved hands injecting into a child's shoulder

Image source: Getty Images.

Of course, there are some caveats that could make the short timeline plausible. It isn't clear, for instance, if BioNTech and Pfizer think they need data from all 30,000 patients to gain regulatory authorization or approval. If the difference between subjects given the coronavirus vaccine and those given placebo are strong enough, it's possible regulators could give a thumbs up based on data from a subset of patients treated early in the study.

It also isn't entirely clear if the companies plan to file with data showing the vaccine creates antibodies, which can be generated fairly quickly after the booster shot, or whether regulatory agencies will require companies to show a difference in the rate patients develop COVID-19 after treatment with the vaccine or placebo.

Ironically, the inability to control the COVID-19 outbreak in the U.S. works in vaccine-makers' favor because the higher the COVID-19 rate for patients receiving placebo, the easier it is for them to show that the vaccine lowers that rate.