Pfizer says coronavirus vaccine study still on track for October readout

Dive Brief:

  • A closely watched late-stage study of Pfizer’s experimental coronavirus vaccine remains on track to deliver initial results by the end of October, company CEO Albert Bourla affirmed Tuesday, despite a slowing rate of infections in the U.S.
  • Just over 29,000 people had enrolled in the Phase 3 study by last Friday and, as of Monday morning, 12,000 of them had received the second shot in the two-dose regimen used for Pfizer’s vaccine. The pharma and partner BioNTech recently asked the Food and Drug Administration for clearance to expand the trial to include 44,000 participants. 
  • In an unusual disclosure, Pfizer also shared Tuesday safety results through late August for several thousand of the volunteers in the trial on a “blinded” basis, meaning the company hasn’t been informed whether they received the vaccine or placebo. Data showed reported side effects were generally mild to moderate. 

Dive Insight:

Pfizer’s update on its vaccine trial, tucked into a two-day investor briefing, didn’t change the timeline for when the company first expects to have results.

The drugmaker has enrolled patients in its Phase 3 trial in the U.S. slightly faster than fellow frontrunner Moderna, and a readout in late October would likely make Pfizer and partner BioNTech the first to discuss an authorization or approval with regulators in the U.S.

But Pfizer’s progress report is more notable following a pause to trials of a vaccine developed by AstraZeneca and the University of Oxford, which were viewed as among the furthest along in testing before an unexplained illness in one U.K. participant triggered a safety review

While AstraZeneca has shared little information on the volunteer’s illness, CEO Pascal Soriot reportedly said her symptoms were consistent with transverse myelitis, an inflammation of the spinal cord that can damage the protective coating for nerve cell fibers. Transverse myelitis can be caused by viral infections and therefore is of concern for researchers studying vaccines. 

U.K. health authorities have cleared trial sites in the country to resume vaccinations with AstraZeneca and Oxford’s shot, but a large study in the U.S. remains on hold. 

In presentations Tuesday, Pfizer executives detailed the safety monitoring in place for their trial and disclosed that the independent study committee had not recommended pausing or discontinuing study of the vaccine at any point. The committee, which is composed of vaccine experts, reviews unblinded study data weekly.

Blinded results shared by Pfizer Tuesday showed fatigue, headache, muscle pain and chills were the most common side effects following vaccination or administration of placebo. Since the trial is ongoing, neither study investigators nor the company know which participants got Pfizer’s shot. 

Pfizer and BioNTech’s expectations of a late October data readout could put the companies at the center of a brewing controversy over whether the Trump administration would pressure the FDA to clear a vaccine before the election.

Both drugmakers last week signed an unusual pledge from vaccine developers to not ask for an authorization or approval until having results in hand that convincingly show safety and effectiveness — a vow Pfizer’s Bourla reiterated Tuesday. 

Late October may still prove too aggressive a timeline, should fewer participants than expected fall ill with COVID-19. Bourla did note a slowing infection rate in the U.S. Tuesday, but said Pfizer’s forecast included current trends in cases. 

Pfizer executives said their trial could be ruled a success if the vaccine exceeds 60% effectiveness over placebo in preventing COVID-19, which would meet a standard recently set out by the FDA for an approval. 

The bar for an emergency authorization is less clear, although the agency has said it plans to soon issue guidance. 

Pfizer and BioNTech’s shot, like Moderna’s, is based on messenger RNA technology that’s designed to spur the body’s cells to train the immune system against SARS-CoV-2. The technology has proven fast to deploy during the pandemic, but no mRNA vaccine has been cleared for any infectious disease. 

Pfizer and BioNTech expect to be able to supply 1.3 billion doses of their vaccine next year, if studies prove it safe and effective.

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