A powerful advisory panel of the Food and Drug Administration argued Friday that boosters should be authorized by the agency. Johnson & JohnsonTo the over 15 million Americans that have had the first dose of Covid-19, a single-shot shot is available.

The unanimous vote – by the agency’s Vaccines and Related Biological Products Advisory Committee – is a critical step before the U.S. can begin giving second shots to J&J recipients, some of whom have said they are anxious to get the additional protection. One dose of J&J’s vaccine has been shown in studies to be comparatively less effective than the two-dose messenger RNA vaccines made by Pfizer–BioNTechAnd Moderna. The panel recommended the doses to everyone 18 and over who’s already received J&J’s first shot with many committee members saying it should be considered a two-dose vaccine much like Moderna and Pfizer’s.

This committee meets on Thursday recommended Moderna booster shotsPeople 65+ and high-risk people, as per guidelines of Pfizer’s vaccine.

The FDA generally follows the advice from the committee. A final decision could be made by the FDA’s regulators within days. Although the FDA isn’t final authority, it can give its approval. Next week, a Centers for Disease Control and Prevention vaccine advisory group will decide who should get the extra J&J shots. Booster shots may be given immediately if it makes a recommendation to Dr. Rochelle Wilensky, CDC Director.

J&J, which received authorization for its vaccine in late February, asked the agency to approve a booster shot of its one-dose vaccine for people ages 18 and older on Oct. 5. Data has been submitted by J&J that shows that the second dose is comparable to the performance of the mRNA vaccines. It boosts the protection against symptomatic infections from 72% up to 94% two months after its first dose.

FDA scientists were present at the Friday meeting days in advance. published an analysis on J&J’s application for a booster, questioning the strength of the data. Although the FDA acknowledged that people could benefit from another dose of the vaccine, it noted that the FDA had not verified the data and limited information was available. It acknowledged a single J&J dose was consistently less effective than the mRNA vaccines in clinical trials and in real-world studies.

Some members of the committee asked FDA if they would be able to postpone the decision regarding boosters. The FDA replied that it was too soon because there were still many questions. Other members wondered why the agency brought J&J’s application before the committee before it was able to verify all of the data.

Is it possible to say that the deadline is a bit early?” There are a number of issues that are still outstanding,” said Dr. Cody Meissner of Tufts University. There are many uncertainties at the moment, which makes it difficult for voters to cast a vote tonight.

In explaining the speediness of the review, committee Chair Dr. Arnold Monto noted the lower performance of J&J’s one-shot vaccine compared with Pfizer and Moderna’s.

His words were, “There is an urgent public health need here.”

FDA officials acknowledged during their presentations before the panel that J&J’s trials were completed with small sample groups of participants, making it difficult to draw conclusions on the data. Dr. Peter Marks (the agency’s top vaccine regulator) asked that the panel continue with their meeting and address any outstanding concerns.

Dr. Johan Van Hoof, a J&J vaccine development executive, told the committee that boosters administered six months after the primary dose resulted in a 12-fold increase in antibodies.

Van Hoof explained that the boosters were administered six months after the initial vaccination. The vaccine was also more effective against Covid variants including the extremely transmissible delta strain. Based on data from 17 people aged between 18 and 55, the data was compiled by Van Hoof. A larger study of 51 trial participants saw a nearly 5-fold increase in antibodies from a J&J booster given two months after the first dose.

The 17 participants in J&J’s six-month trial experienced no new adverse side effects, FDA medical officer Dr. Timothy Brennan told the agency’s advisory committee. Of the participants, roughly 47% reported headache symptoms, 26% reported fatigue and 21% reported myalgia, or muscle pain, after receiving a J&J booster.

There is no data to suggest people are at increased risk of a rare, but serious, blood clot condition after receiving a second dose of J&J’s vaccine, according to J&J executive Dr. Macaya Douoguih.

She presented data from the U.K. on second doses of AstraZeneca’s vaccine, which uses a similar platform to J&J’s. Data shows that the incidence of vaccine-induced immunothrombotic therapy (VITT) after the second dose is lower than it was the first.

Douoguih explained that even though the vectors might not all be the same, data could give some clues into the potential risk.

This story is still in development. Stay tuned for new updates.