FDA spells out guidelines for approving Covid-19 vaccines

Sarah Owermohle

The FDA on Tuesday released final guidance laying out its standards for approving coronavirus vaccines, requiring that any vaccine candidate be at least 50 percent more effective than a placebo.

The agency also left open the possibility it would issue an emergency use authorization for a vaccine, but it said making that decision before the completion of large, randomized clinical trials could make it harder to determine a vaccine's effectiveness.

Background: Vaccines against the coronavirus are being developed in record time. Multiple manufacturers have said they could have answers on their shots by the end of this year and are scaling up manufacturing with the expectation that they would quickly need to churn out millions of doses.

FDA said it could issue an EUA if the agency feels there is enough data on safety and efficacy, but its preference is that vaccines undergo more vigorous scientific review. FDA recently revoked another set of EUAs that cleared hydroxychloroquine and chloroquine to treat Covid-19, after the data for that decision was questioned and clinical trials showed the antimalarial drugs didn't work.

There has been mounting concern from public health experts that FDA could make a hasty decision on an eventual vaccine, but Tuesday's guidance may assuage some of those concerns. House Speaker Nancy Pelosi in a statement called the guidelines "critical to ensuring that Americans can have confidence that any vaccine that is approved for the U.S. will be effective and safe."

The details: FDA said in order to ensure a widely deployed Covid-19 vaccine is effective, it needs to show at least 50 percent efficacy in a placebo-controlled clinical trial. Before approval, manufacturers will also need to conduct animal studies to ensure that their candidates don’t provoke an immune response that actually worsens the infection, known as enhanced respiratory disease.

The agency said development can be sped up through creative clinical trial designs that allow for scientists to adapt dosing and options based on rolling data. Those designs, known as adaptive or seamless trials, are fleshed out in the guidance.

FDA said it will also be important to study vaccine candidates in patients with confirmed infections, since many people seeking out a vaccine may had already unknowingly contracted the virus without experiencing symptoms.

The agency said Covid-19 vaccines must meet all the standard laws and regulatory requirements for any other vaccines to be approved, including manufacturing and control requirements.

What’s next: One of the leading vaccine candidates, developed by NIH and Moderna, is slated to begin phase III trials in July. Moderna’s CEO has said that if early data is positive, it could begin dosing health care workers in the fall. Other drugmakers, including Johnson & Johnson and Pfizer, have said they could have millions of doses ready by early 2021 if their data is positive.