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Yesterday, the FDA's vaccine advisory committee dedicated the entire day to reviewing the outcomes of Pfizer and BioNTech's COVID-19 vaccine trials. By the end of their deliberations, they unanimously agreed that the scientific evidence indicates the vaccine's benefits surpass its potential risks. The FDA is anticipated to swiftly issue an Emergency Use Authorization (EUA); initially slated for completion by Saturday, the authorization might be granted as early as this evening, as reported by the New York Times.
Does this imply the vaccine has been fully approved?
Not quite. While an EUA is likely within days, full approval may still take several months. An EUA serves as a provisional authorization, permitting vaccine distribution during a public health crisis. Over time, the EUA could be modified or revoked.
Full approval, as traditionally understood for vaccines or drugs, entails additional bureaucratic steps such as factory inspections. The FDA will also likely require further data on long-term efficacy and safety across diverse demographic groups.
What comes after this?
While a 'yes' vote from an advisory panel doesn't ensure immediate action, the FDA stated in a recent press release that it 'will swiftly move to finalize and issue an emergency use authorization.' In short, it's on its way.
The vaccine manufacturer, along with federal and state authorities, has already collaborated with hospitals and healthcare providers to prepare for vaccine distribution. Essentially, a hospital near you might already have a high-tech container filled with COVID-19 vaccine doses. Once authorized, they are prepared to begin administering the shots immediately.
This entire process may repeat next week, as the FDA panel is scheduled to convene on Thursday, the 18th, to evaluate an EUA for Moderna’s vaccine.
Who will be prioritized for the initial vaccinations?
This determination is made at multiple levels. Initially, the CDC's advisory committee, ACIP, which formulates vaccine guidelines, has already suggested that healthcare professionals and nursing home residents will likely be the first to receive the vaccine.
The committee is scheduled to convene today and again this weekend following the issuance of the EUA. (You can listen to these meetings here, if interested.) Their prior discussions focused on COVID-19 vaccines broadly, but today they will specifically examine the Pfizer/BioNTech vaccine, utilizing the latest trial data.
While ACIP establishes recommendations and the federal government allocates doses to vaccine jurisdictions (typically each state), the states ultimately decide how to distribute their allotted vaccine doses.
What uncertainties still exist?
Numerous questions remain. What we do know is that the Pfizer/BioNTech vaccine, an mRNA-based formulation, successfully shielded trial participants from the coronavirus. Those aged 16 and older were monitored for an average of two months following their second dose (the vaccine requires two doses), and no severe side effects or safety concerns were identified.
For more details on safety and effectiveness, a paper outlining the phase 3 trial results was published in the New England Journal of Medicine yesterday. Alternatively, you can review the FDA’s briefing document, which provides additional context about the agency’s evaluation process.
Overall, the study findings appear highly promising. However, there is limited information on aspects not covered in the research. Some key uncertainties include:
Does this vaccine block asymptomatic infections?
In the study, a COVID case was defined as at least one symptom paired with a positive PCR test. Thus, while the vaccine effectively prevents illness, it’s unclear if it also stops infection. (Pfizer mentioned that human trials addressing this question are ongoing, and animal studies indicated it may prevent infection.)
Preventing asymptomatic transmission is vital for achieving herd immunity. If vaccinated individuals cannot contract or transmit the virus, widespread vaccination will halt COVID-19's spread. Even those who cannot or choose not to get vaccinated will benefit indirectly, as the virus will struggle to circulate.
However, if the vaccine only prevents severe illness without stopping infection, the situation changes. While individuals would be protected, the virus could still spread widely within the community. Vaccinated people would be less vulnerable to severe outcomes, but the virus would continue to circulate unchecked.
Is this vaccine safe for children?
The trial initially included only adults before expanding to 16 and 17-year-olds. While this group fared well, they represented just 150 participants out of approximately 40,000. Some advisory panel members expressed concerns that children might react differently to the vaccine, especially since their immune systems can occasionally respond unpredictably and severely to COVID-19.
A Pfizer representative stated that with sufficient safety data for 16 and 17-year-olds, the company has begun testing the vaccine in 12 to 15-year-olds. If results are positive, they plan to extend trials to 5 to 11-year-olds, followed by younger children. However, this comprehensive process could span months or even years.
Is this vaccine safe for use during pregnancy?
Pregnant individuals were excluded from the trials, creating a familiar dilemma with new medical treatments: reluctance to test on pregnant populations leaves them with the choice of using (or avoiding) a treatment that lacks pregnancy-specific data.
This presents a complex risk/benefit analysis. COVID-19 poses heightened risks to pregnant individuals and their fetuses, yet without sufficient data, the vaccine's safety during pregnancy remains uncertain. A Pfizer representative noted that they are monitoring pregnancies that occurred during the trial and conducting animal studies to gather more insights, with results expected soon.
What’s the situation with the severe allergic reactions reported in the UK?
Following the UK’s authorization of the vaccine earlier this week, two individuals experienced severe allergic reactions on the first day of public vaccinations. Both had a history of severe allergies, though specifics about their triggers remain unclear. As a precaution, the UK now advises against vaccinating individuals with a history of anaphylaxis or those who carry an epi-pen due to severe allergies.
The Pfizer/BioNTech trials did not identify any similar issues; they excluded individuals with allergic reactions to vaccines or their components but not those with general allergies. The two cases in the UK might be anomalies, or they could indicate a genuine concern for people with allergies. This remains uncertain.
The real-world population will differ from trial participants
Additional surprises, like the allergy issue, may arise. Groups underrepresented in the trials, such as individuals with severe health conditions, were only included if their conditions were stable. However, those at high risk for COVID-19 complications often have more serious health issues than trial participants.
It’s also unclear if a single dose could be nearly as effective as two, as the study only evaluated a two-dose regimen. The duration of vaccine protection is unknown, given the limited two-month follow-up data. Long-term, placebo-controlled data may also be compromised, as ethically, placebo group participants should be offered the vaccine once available. Regulators expressed concern, but in this landscape of uncertainties and tradeoffs, the results so far are promising. This article was updated at 1:19 p.m. EST on Dec. 11 to reflect late-breaking changes to the timeline for the Pfizer and BioNTech COVID vaccine EUA from the FDA.
