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Single-Dose J&J Vaccine Is 66 Percent Effective in Clinical Trials

Johnson & Johnson files with the U.S. Food and Drug Administration for emergency use authorization

A medical worker prepares documents inside the laboratory during a phase 3 trial of the Johnson & Johnson Covid-19 vaccine

Bloomberg / Getty Images

A medical worker prepares documents inside the laboratory during a phase 3 trial of the Johnson & Johnson COVID-19 vaccine.

En español | Americans could see a third COVID-19 vaccine available to combat the pandemic if the federal government authorizes the use of a single-dose Johnson & Johnson (J&J) product that company data shows is 66 percent effective against moderate to severe illness.

J&J filed an application with the U.S. Food and Drug Administration (FDA) for emergency use authorization of its vaccine late Thursday.  If it receives an EUA, the J&J product would be the third COVID-19 vaccine available in the United States. Millions of Americans have already received vaccines produced by Pfizer-BioNTech and Moderna. The FDA has said that a COVID vaccine would have to be at least 50 percent effective in order to be authorized.

Based on the process followed for the first two vaccines, an EUA could come within weeks. An independent FDA panel will review the J&J data and is scheduled to meet on Feb. 26 to discuss the EUA. If the authorization is granted, an advisory committee of the Centers for Disease Control and Prevention (CDC) would meet to recommend how the vaccine should be used. The federal government has contracted with J&J to deliver 100 million doses of its vaccine by the end of June, if it is approved.

The data from its phase 3 clinical trials involving nearly 44,000 participants from the U.S. and abroad also shows that the J&J vaccine was 85 percent effective in preventing severe cases of COVID-19. The company also reported that the vaccine completely prevented hospitalizations and deaths among those in the trial who actually received the vaccine and not a placebo.


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J&J's trial did not reveal any significant safety concerns, with only 9 percent of those participating in the clinical trials reporting a fever. There were no cases of a severe allergic reaction to the shot.

"The results are very encouraging,” Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health (NIH), said at a White House COVID response team briefing last week. “This tells us that we have now a value-added additional vaccine candidate. This has important potential and real implications both domestically and globally."

The trial data shows different results in different parts of the world. While the overall effectiveness is 66 percent, it was 72 percent among U.S. participants. But in Latin America and South Africa, where new variants of the coronavirus have taken hold, the vaccine's effectiveness was 66 percent and 57 percent, respectively.

What's different about this vaccine

This vaccine differs from the Pfizer-BioNTech and Moderna vaccines in that it calls for only one shot and can be stored in a conventional refrigerator as opposed to the two shots and colder storage temperatures that the other vaccines require. Both of the two-shot vaccines were shown to be about 95 percent effective.

William Moss, executive director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health, said in an interview with AARP before the J&J data was released that he didn't expect the efficacy for that one-dose vaccine to be as high as the Pfizer-BioNTech and Moderna products. He called the effectiveness of those two vaccines “astounding."

And Moss said Friday that he understands that while many people may prefer the vaccines with the higher efficacy, what's most important is to get as many people vaccinated as soon as possible. “I have no doubt that two doses would provide higher antibody levels,” Moss said. “I think the question is, in the midst of a pandemic, whether that trade-off is worth it."

"Certainly, this single dose is better than no dose,” Moss added. J&J did begin a two-dose clinical trial in November, and Moss said that he suspects there may eventually be a two-dose J&J vaccine regimen.

How these vaccines are made

All COVID-19 vaccines are designed to stimulate people's immune systems to produce antibodies to the protein on the surface of the coronavirus, commonly referred to as the spike protein.

What's different about the Moderna and Pfizer-BioNTech vaccines on the one hand and the J&J product on the other is the way they get the genetic code into our cells that will allow the immune system to learn to recognize and block the real coronavirus.


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Moderna and Pfizer-BioNTech use what's called messenger RNA, or mRNA, to give our cells the genetic instructions. The J&J vaccine instead uses a harmless adenovirus to deliver the instructions to our cells to produce the spike protein found on the surface of the coronavirus.

In each case, when our cells recognize the spike protein, they can create antibodies to block it from infecting our bodies.

Both of these vaccine strategies are relatively new, Moss said. The J&J vaccine uses the same technology that the company used to produce an Ebola vaccine that was approved by the FDA last summer.

Dena Bunis covers Medicare, health care, health policy and Congress. She also writes the “Medicare Made Easy” column for the AARP Bulletin. An award-winning journalist, Bunis spent decades working for metropolitan daily newspapers, including as Washington bureau chief for the Orange County Register and as a health policy and workplace writer for Newsday.

Editor’s note: This story has been updated to reflect J&J’s filing for emergency use authorization (EUA) of its vaccine.

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