Moderna COVID-19 vaccine passes FDA reviewers' test, but shares drop anyway

Moderna’s COVID-19 vaccine is checking the boxes en route to an emergency nod. FDA staffers endorsed the shot as safe and effective in briefing documents published (PDF) on Tuesday, ahead of a COVID-19 vaccine advisory committee meeting scheduled for Thursday.

The documents confirmed the safety and efficacy profile of the vaccine, mRNA-1273, reiterating that it was 94.5% effective at preventing COVID-19 infection at least two weeks after vaccination with no serious safety concerns. The vaccine is given in two doses one month apart.

Moderna’s request for Emergency Use Authorization is based on interim data submitted on Nov. 7, but it has since provided the FDA with updated data showing it was 94.1% effective. It broke down the latest data, from its final scheduled analysis, finding the vaccine was 95.6% effective in adults under 65 and 86.4% effective in adults 65 and older.

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Its updated data suggest that the vaccine could prevent asymptomatic infections after the first dose, Moderna said in an addendum to its own briefing documents (PDF). The investigators swabbed patients for SARS-CoV-2, the virus that causes COVID-19, before they received the first dose and the second dose of the vaccine. Among patients who entered the trial without prior exposure to COVID-19, 14 patients in the vaccine group and 38 patients in the placebo group had asymptomatic infections when they came back for their second dose.

“This suggests mRNA-1273 might be slowing this important group who are walking around w/ no symptoms,” Jefferies analyst Michael Yee wrote in a note to clients on Tuesday.

Safety results from more than 30,300 participants turned up “no specific safety concerns… that would preclude issuance of an EUA,” FDA staffers wrote in the report.

The most common side effects were pain, fatigue, headache and muscle pain. Serious side effects, including heart attack, gallbladder inflammation and kidney stones were rare, together affecting 1% of patients in the vaccine group and 1% of patients in the placebo group.

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Three patients in the vaccine group and one in the placebo group reported facial paralysis, or Bell’s palsy, but the FDA staffers noted they didn’t have enough data to “determine a causal relationship with the vaccine.”

These cases of paralysis were “similar to the 4-0 imbalance” Pfizer and BioNTech saw in the data for their COVID-19 vaccine, Yee wrote.

“Some background work suggests evidence that Bell's palsy may be a reaction to a viral infection, is characterized by muscle weakness that causes one half of the face to droop (but resolves) and may be from reactivation of an existing dormant viral infection,” Yee added.

The vaccine’s safety profile was “generally similar” across age groups, genders, ethnic and racial groups, the staffers wrote. The study participants were 79.5% white, 9.8% Black or African American, 4.4% Asian, 0.8% American Indian or Alaska Native and 0.2% Native Hawaiian or other Pacific Islander. One-fifth of the participants were Hispanic or Latino.

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The vaccine’s next stop will be an advisory committee meeting, where outside experts will discuss its data and vote on whether to recommend it for emergency authorization. This comes one week after the committee convened to discuss Pfizer and BioNTech’s prospect, voting 17-4 that its benefits outweighed its risks. The FDA granted the EUA on Friday, the following day.

Given that the FDA’s briefing documents on Moderna’s vaccine are “nearly identical” to those about Pfizer and BioNTech’s shot, Yee expects the advisory panel to vote in mRNA-1273’s favor.