FDA advisers to consider third possible Covid-19 vaccine Friday

US Food and Drug Administration vaccine advisers are scheduled to meet Friday to discuss the potential emergency authorization of a third coronavirus vaccine for the US, this one made by Johnson & Johnson's vaccine arm Janssen Biotech.

It's the next step in a process that could end with the new vaccine's rollout early next week. As with the two currently authorized vaccines, advisers and federal agencies are meeting over a weekend to try to get the vaccines to the US public as soon as possible.

The FDA has already considered the advanced, Phase 3 clinical trial testing data presented by Janssen and says it shows the vaccine is safe and effective. The Vaccines and Related Biological Products Advisory Committee or VRBPAC is made up of vaccine experts and other medical professionals, industry and consumer representatives who will consider presentations from FDA about its findings, as well as from Janssen.

They'll also hear the latest from the Centers for Disease Control and Prevention about the spread of the virus, including worrying new variants, and on the CDC's surveillance for any safety worries from the currently authorized vaccines made by Pfizer/BioNTech and Moderna.

The VRPBAC will vote Friday on whether to recommend FDA emergency use authorization (EUA), and the FDA will then take that vote into consideration in deciding whether to authorize the vaccine.

That decision could come very quickly after the VPBPAC vote.

On Sunday, a second advisory group weighs in. The CDC's Advisory Committee on Immunization Practices will look at all the same data and will discuss whether people should get the vaccine and if so who, and when. A vote is expected by 3 p.m. ET from ACIP.

The CDC then takes the ACIP vote into consideration and the CDC director -- who is currently Dr. Rochelle Walensky -- will decide whether the vaccine has her agency's OK.

Typically, this is a slow and deliberative process, but the schedule was sped up because of the urgency of the pandemic. The authorization and subsequent CDC nod for the Pfizer/BioNTech and Moderna vaccines in December each took place over a period of days.

After that, distribution can begin. The White House has promised to begin immediately, with 2 million doses going to states and the rest directly to pharmacies and community health centers. The federal government has said it expects to have up to 4 million doses of Johnson & Johnson vaccine on the first day. The company has promised to ramp up production to deliver 20 million doses by the end of March and 100 million doses by the end of June.

While Pfizer and Moderna's vaccines require two doses for full efficacy, the Johnson & Johnson vaccine requires only one dose, although the company is testing at two-dose regimen to see if it works any better.

Johnson & Johnson's data indicates its vaccine was 66% effective across all global trials in preventing moderate to severe Covid-19 disease 28 days after immunization. It was 85% effective in preventing severe disease. No one who got the vaccine died from Covid-19.