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FDA’s Marks: Stricter Standards for COVID-19 Vax Were by Design

The FDA’s stricter standards for a COVID-19 vaccine are meant to reassure the public about the safety and efficacy of a vaccine, and end the politicization of vaccine standards, the FDA’s top official for vaccines said Wednesday.

Data from phase III studies with a median follow-up duration of at least 2 months, and at least five severe COVID-19 cases in the placebo group, were standards proposed by the FDA for weeks. These standards were released in briefing documents the FDA made available to the public Tuesday.

Peter Marks, MD, PhD, director of the FDA Center for Biologics Evaluation and Research, emphasized the importance of tracking safety of the vaccine during an American Medical Association webinar on Wednesday.

“We asked for a median of 2 months of safety follow-up after the final vaccination of the population enrolled in the trial,” he said, explaining that when looking at adverse events, such as Guillain-Barre syndrome and transverse myelitis, they tend to occur within a median of 2 months or before.

“Some people would like longer than that, some people would like shorter than that [but] … that seems like a reasonable compromise,” he added.

Notably, President Trump lodged his objection on Tuesday night, calling the standards a “political hit job,” and saying they “make it difficult for them to speed up vaccine approvals before Election Day,” though the White House did approve the new standards.

In the webinar, Marks discussed the importance of clinical outcomes for COVID-19 vaccines. With other diseases, “we understand the correlates of protection,” and how that correlates with clinical outcome. These are not yet known for SARS-CoV-2.

“We expect these vaccines to reach clinical endpoints versus immunologic endpoints,” he said, noting that hopefully once the first couple vaccines are approved, the correlates of protection will become clearer.

Commenting on the new guidelines, Matthew Spinelli, MD, of University of California San Francisco, noted the line in the document where the FDA said it advised sponsors the agency “would not consider availability of a COVID-19 vaccine under emergency use authorization (EUA), in and of itself, as grounds for stopping blinded follow-up in an ongoing clinical trial.”

“It is very important that we continue follow-up to understand duration of protection, safety, long-term efficacy even if EUA issued,” Spinelli told MedPage Today via email. “My hope is that clinical trials that are sufficiently large are performed with adequate sample size and follow-up to ensure there are no safety signals.”

Marks said one of the “core pieces” of the FDA guidance was that the vaccine must be 50% more effective in preventing SARS-CoV-2 infection, though he stated a vaccine with 70%-80% efficacy, and 70-80% of people taking it, could bring about herd immunity.

Spinelli also noted the efficacy point estimate the FDA is targeting is similar to the seasonal flu vaccine.

Marks would not completely rule out an EUA, saying, it was at the “outer realm of possibility” that a vaccine could reach the number of clinical events needed by the end of