Within the next week, Pfizer (PFE 0.11%) and BioNTech (BNTX 2.23%) expect to reach their goal of enrolling 30,000 participants in the phase 2/3 clinical trial testing their coronavirus vaccine, BNT162b2.

How are they planning on celebrating? By enrolling another 14,000 participants.

While Pfizer and BioNTech have zoomed into the front-runner spot in the coronavirus race, they're also smartly playing the long game, realizing that safety and efficacy data in distinct populations will drive sales beyond the initial bolus of patients.

On Saturday, the drug makers said they submitted a proposal to the Food and Drug Administration to amend the protocol for their study, increasing enrollment to 44,000 participants.

Pfizer and BioNTech plan to use the expanded enrollment to test the coronavirus vaccine in patients who are infected with HIV, hepatitis C, or hepatitis B viruses, as well as increase the diversity of the clinical trial. The expanded population will also allow for additional evaluation of the safety and efficacy of BNT162b2.

Gloved hands giving an injection into a shoulder

Image source: Getty Images.

The enrollment of the additional participants will help determine if there are any specific issues with efficacy and safety in the populations, but it shouldn't affect the initial data readout -- the companies still expect to have data by the end of October, assuming current infection rates hold.

Pfizer and BioNTech managed to enroll their phase 2/3 clinical trial faster than Moderna (MRNA 3.06%), which had enrolled 23,497 participants of the expected 30,000 in the phase 3 study testing its coronavirus vaccine, mRNA-1273, as of its latest update on Friday. Moderna appears to have slowed enrollment in order to increase the diversity of the participants in its clinical trial, perhaps giving it an edge in sub-populations just as Pfizer and BioNTech are looking to do with their expanded population.