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Pfizer and BioNTech are moving to enlarge the Phase 3 trial of their Covid-19 vaccine by 50%, which could allow the companies to collect more safety and efficacy data and to increase the diversity of the study’s participants.

The companies said in a press release that they would increase the size of the study to 44,000 participants, up from an initial recruitment goal of 30,000 individuals.

The U.S. Food and Drug Administration will have to approve the change before it goes into effect.


“The companies continue to expect that a conclusive readout on efficacy is likely by the end of October,” the press release said. The Pfizer and BioNTech study is likely to be among the first in the U.S. to report efficacy data from a Phase 3 trial.

Expanding the trial will likely make it easier for the company to demonstrate whether the vaccine is effective against SARS-CoV-2, the virus that causes Covid-19. The companies also said that the change will allow the study to include a more diverse population. The companies said the study will now include adolescents as young as 16, people with stable HIV, and those with hepatitis C or hepatitis B.


The companies said that the trial is expected to reach its initial target of 30,000 patients next week. Moderna, which started its trial on the same day as Pfizer, said on Sept. 4 that it is working to increase the diversity of trial participants in its study, “even if those efforts impact the speed of enrollment.”

The Pfizer/BioNTech study could finish sooner than Moderna’s, even though the two began on the same day, for other reasons, as well. Both vaccines require a second shot; Pfizer’s is given after three weeks, while Moderna’s is given after four. The Pfizer trial also starts to count cases of Covid-19 sooner after participants receive their shots than the Moderna study.

But the Pfizer/BioNTech vaccine could also prove to be one of the most difficult of the experimental vaccines to distribute, should they prove effective. The vaccine must be kept at a temperature of -70 degrees Celsius.

There has been political pressure to move a vaccine quickly, with President Trump saying that one could be available before election day. Last week, several drugmakers, including Pfizer, issued a pledge not to move a vaccine forward sooner than was justified by the results of their clinical trials.

  • Can we read into this anything about the results of the current trial?

    It seems to me that they would not expand the trial unless it was producing positive results. Or, at least it is not producing negative results.

    There was an editorial today advocating for an EUA for a vaccine for certain groups. I’d guess that this is Pfizer’s response to that idea. If they work quickly, those limitations could be moot.

  • I would hope that any President, regardless of politics, would “agressively” try and get a vaccine AS SOON AS SAFELY POSSIBLE?

    Do you honestly think that multi-billion dollar multi-national pharma companies would risk massive $$$$$ potential libility in lawsuits by pushing out an unsafe vaccine just because the President wants it?

    Dale, let’s be honest, do you think that if this was not an election year the Democrats would “aggresively” be rooting against a vaccine and actively encouraging people not to get the vaccine, potentially risking thousands of lives?

  • Dale, are’nt YOU a positive person! I wish you luck in your life! I am not being sarcastic; I feel bad for you!

  • You are missing the fact that Phase 1 and Phase 2 trials have gone splendidly, and it won’t get approved until Phase 3 trials also go well. Other countries also have vaccines on the horizon. Vaccines aren’t that difficult to make. It’s not about politics – it’s about science.

  • Fauci is part of big Pharma. Dr. Gottlieb is on the board at Pfizer he has a conflict of interest and pushes for a locking down until there is a vaccine. You watch Fauci make millions joining the boards of big pharma.

    • Big Pharma makes so much more money on medications for infected and hospitalized Covid patients than they’ll ever make on a vaccine, at least at the suggested price points. If you get hospitalized with the virus will you accepts treatment with new drugs such as Remdesivir?

  • The Phase-3 data will be published for your reading enjoyment, if you don’t trust the FDA. Of course, you won’t read the Phase-3 data, and will continue to spread vaccine skepticism that will literally kill people.

  • Who cares the reason why the vaccine is being fast tracked.. love for humanity, fear of becoming ill, profit, political gain, etc. As long as it’s safe, as far as I’m concerned we need it ASAP.

  • Let’s be honest
    Do u think that if this was not an election year that the President would be as aggressive in trying to get a vaccine by November 1st?

  • I want to point out that political pressure doesn’t affect this vaccine nearly as much as media articles portray. This vaccine is being developed by BioNTech *in partnership* with Pfizer. BioNTech is a German company with no political agenda in the US. The company is also in partnership with Fosun Pharma, a Chinese company, for the same vaccine.

    • Yea right genius, but the companies making and testing the vaccine have limited involvement with its approval. In the US, prescription drugs are approved under the sole authority of the FDA, and the head of the FDA is a political appointee.

      What am I missing?

    • Let’s be honest
      Do u think that if this was not an election year that the President would be as aggressive in trying to get a vaccine by November 1st?

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