Pfizer Vaccine Inches to Approval; More Questions Raised over AZ’s Shot

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The Pfizer / BioNTech vaccine for Covid-19 has taken another big step forward after the FDA released the findings of its safety report. This document will provide the information needed for the FDA’s Vaccines and Related Biological Products Advisory Committee, slated to meet this week, to decide whether to grant an Emergency Use Authorization for the vaccine.

The vaccine

The vaccine, a joint project by US-based pharmaceutical firm Pfizer and Germany’s BioNTech, is one of the first to be delivered to the general public. Pfizer revealed in a press release that the vaccine has been shown to be more than 90% effective at preventing Covid-19 and has no serious safety concerns. Patients will require two doses, administered three weeks apart, to achieve the 90% effectiveness. The vaccine must be stored at extremely cold temperatures (the recommended storage environment is -70°C), which presents challenges for widespread distribution.

The safety review

The FDA’s Briefing Document offers an examination of the information Pfizer provided to the agency. The data comes from a stage-3 clinical trial on 44,000 participants. The safety data Pfizer covered 38,000 of those participants, split evenly between placebo and vaccine groups. The information was recorded through November 14, 2020 and included two-months of follow-up data.

The results

The vaccine starts working a week after the first dose. In the trial, 162 people became infected with Covid-19  in the placebo group and 8 who received the actual vaccine. It appears to be similarly effective regardless of age, gender, ethnicity, and the presence of comorbidities. The briefing also suggests that the vaccine could help prevent repeat infections.

While there were “no specific safety concerns identified that would preclude issuance of an

EUA,” that doesn’t mean the vaccine is without side effects. According to the briefing:

“The most common solicited adverse reactions were injection site reactions (84.1%), fatigue (62.9%), headache (55.1%), muscle pain (38.3%), chills (31.9%), joint pain (23.6%), fever (14.2%); severe adverse reactions occurred in 0.0% to 4.6% of participants, were more frequent after Dose 2 than after Dose 1, and were generally less frequent in participants ≥55 years of age (≤2.8%) as compared to younger participants (≤4.6%). The frequency of serious adverse events was low (0.5%).”

The next steps

An FDA panel is expected to make its decision regarding approval during a meeting on Thursday. This won’t mark the end of safety testing, as both long-term follow-ups of ongoing clinical studies and new studies on health-care workers, pregnant women, military families, and veterans are also planned. The panel will also consider what additional research will be needed moving forward.

Pfizer’s vaccine isn’t the only one in development. A similarly effective vaccine from rival firm Moderna is also nearing approval. A third vaccine candidate, from Oxford University and pharmaceutical giant AstraZeneca, is facing increased scrutiny from regulators and concerns among the scientific community over dosing issues and the trial’s failure to test one particular dose that showed high efficacy on those over 55. The New York Times reported yesterday, December 8, that some participants did not receive the required second dose for 3 months. By study protocol, it should have been given one month after the initial shot.

The UK has already approved the Pfizer vaccine and recently began administering it to elderly and vulnerable persons. The FDA panel’s review of the Moderna vaccine is scheduled for December 17th ; the AstraZeneca vaccine is not yet ready for review.

The take home

While the vaccine has not yet been given emergency use approval, passing this review is a big step toward that milestone. Should the EUA be granted, vaccination could begin soon, much as it has in the UK.

Sean Marsala is a health writer based in Philadelphia, Pa. Passionate about technology, he can usually be found reading, browsing the internet and exploring virtual worlds.

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