FDA to set high bar for emergency COVID-19 vaccine approvals

The FDA is set to take a tough line on the evidence required to support emergency use authorization (EUA) of COVID-19 vaccines, according to The Washington Post. The reported requirements suggest a company is unlikely to have the data needed to support an EUA before the election in six weeks.  

President Donald Trump has repeatedly predicted a vaccine will be ready for the election in the first week of November. The potential political benefits of hitting that target, coupled to events such as the convalescent plasma EUA press conference, have raised concerns that the FDA will come under pressure to authorize a vaccine before the election.

No company is likely to satisfy the requirements for full approval early enough to have a submission reviewed by early November, leaving an EUA as the most probable route to a preelection vaccine. The FDA dedicated just a few paragraphs of its existing COVID-19 vaccine guidance to EUAs, stating little more than that emergency authorization may be appropriate “once studies have demonstrated the safety and effectiveness of the vaccine.”

Guidance in development at the FDA is set to flesh out what that means in practice. Leaks suggest the FDA will consider granting EUA to sponsors that have a median of two months follow-up, starting at the second dose, on their late-phase study subjects. 

That requirement will provide a preliminary evaluation of safety. The FDA is also expected to require that the placebo arm has at least five cases of severe COVID-19, plus cases affecting older people. In the absence of the cases, the FDA is unlikely to be able to evaluate what effect the vaccine is having on infection rates. The FDA is demanding evidence of a 50% reduction in risk for full approval.

The incidence of the virus in the community will dictate when vaccine developers have the efficacy data to support an EUA, making the timing hard to predict. The timeline for having two months of safety data is easier to estimate. 

Pfizer, the current front-runner, was halfway to its original 30,000 enrollment target by late August and gives a second dose 19 to 23 days after the first vaccination. That suggests Pfizer recently gave a second dose to the 15,000th participant in its phase 3, putting it on track to have a median of two months of follow-up by mid-November. Pfizer could be further from that target if it needs a median of two months of data on its expanded, 44,000-subject study population.

In a statement to the Post, Pfizer said it remains on track to have efficacy data next month. Moderna said it is unlikely to have data before November. Exactly what data the companies need to win EUA will become clearer when FDA publishes the guidance. FDA disclosed it is working on the EUA guidance discussed in the Post article earlier this month.