(CNN) — A third Covid-19 vaccine, one made by Johnson & Johnson, could be authorized for use in the United States in the near future.

Data about the single-shot vaccine released Friday, and the company is now collating its data to apply to the US Food and Drug Administration for emergency use authorization.

The vaccine was made through a collaboration of J&J’s Belgium-based vaccine division, Janssen Pharmaceutical, and Beth Israel Deaconess Medical Center, and it works a bit differently.

Here’s what’s known about how it works and how it will fit into the mix of vaccines.

How effective is it?

Johnson & Johnson’s Covid-19 single-shot vaccine was shown to be 66% effective in preventing moderate and severe disease in a global Phase 3 trial, the company announced Friday.

The vaccine is 85% effective overall at preventing hospitalization and death in all regions where it was tested.

Its efficacy against moderate and severe disease ranged from one country to another: 72% in the US, 66% in Latin America and 57% in South Africa. This was measured starting one month after the shot.

In South Africa, 95% of cases in the trial were due to a variant known as B.1.351, which is known to be more contagious and carries mutations that may make the virus less susceptible to the antibody immune response — including antibodies prompted by vaccination.

Even those who got moderate cases of Covid-19 in the trial tended to develop a milder course and fewer symptoms, said Dr. Mathai Mammen, Janssen’s global head of research and development.

From one month after the shot, all hospitalizations and deaths occurred in the placebo group.

How it works

The J&J vaccine is what is known as a non-replicating viral vector vaccine, using a common cold virus called adenovirus 26.

Scientists made this vaccine by taking a small amount of genetic material that codes for a piece of the novel coronavirus and integrating it with a weakened version of adenovirus 26. J&J scientists altered this adenovirus so it can enter cells, but it cannot replicate and make people sick.

AstraZeneca uses a similar platform, but its adenovirus comes from a chimpanzee.

The adenovirus carries the genetic material from the coronavirus into human cells, tricking them into making pieces of the coronavirus spike protein — the part it uses to attach to cells. The immune system then reacts against these pieces of the coronavirus.

“So you’re not being infected with the virus that can give you Covid-19 when you get this vaccine. It just has some of the harmless Covid virus proteins on its surface,” explained Dr. William Schaffner, an internist and infectious disease specialist with Vanderbilt University’s Department of Health Policy. “So essentially it’s a sheep in wolf’s clothing, and when your immune system sees it, it responds to it and creates protection against it and in the future, against the real virus that causes Covid-19.”

The technology used in the Covid-19 vaccine has worked with the Ebola vaccine by Janssen.

How is it different from the other Covid-19 vaccines?

Dr. Paul Offit, the director of the Vaccine Education Center at Children’s Hospital of Philadelphia, said the Moderna, Pfizer and J&J Covid-19 vaccines all take a similar approach, but there is a small difference with the J&J approach.

“In the case of the Moderna and Pfizer vaccine you’re just giving the gene in a lipid nanoparticle or a fat droplet,” Offit said. “In the case of J&J you’re giving the gene in a virus that can’t reproduce itself.”

The J&J vaccine is the only Covid-19 vaccine so far to be given in a single dose. Moderna and Pfizer’s use two. Like Moderna’s, it can also be kept at regular refrigerated temperatures and does not need a deep freeze like Pfizer’s.

 

How does a single-dose shot affect the rollout?

 

A single dose and would be much easier to administer and would mean more people could be vaccinated, as none would need to be set aside to give someone a second shot.

“This advantage goes up in neon,” said Schaffner who believes adding a vaccine like this would “really accelerate” vaccination efforts in the US and around the world.

“If it’s a single-dose vaccine, then a billion vaccine doses would translate into a billion people vaccinated,” said Dr. Dan Barouch of Harvard Medical School, who helped develop Johnson & Johnson’s vaccine candidate on CNN’s Coronavirus Fact vs. Fiction podcast.

 

The cold-chain advantage

J&J’s other advantage is that it can be stored at regular refrigerator temperatures, unlike the Pfizer vaccine, which needs special deep freezers. The vaccine is stable for up to three months at 36 degrees F to 46 degrees F, the company said. That means health care facilities would not have to buy extra equipment to safely store the vaccine.

“If they’re successful, these vaccines would especially be popular in the developing world, because they would be easy to store and administer,” said Dr. Rafi Ahmed, the director of the Vaccine Center at Emory University.

The vaccines would also be popular in rural communities in the US and regular doctor’s offices that may not have access or the budget to afford specialized equipment.

“In other words, we could bring the vaccine to the people,” Schaffner said, “rather than bringing the people to the vaccine.”

What happens next?

The company will request what’s known as an emergency use authorization, or an EUA, from the FDA in early February.

The data will get a close look from the FDA and advisers to the US Centers for Disease Control and Prevention.

While the FDA is reviewing the data, it schedules a public meeting of its Vaccines and Related Biological Products Advisory Committee. The committee is made up of independent science and public health experts who will discuss the J&J data and make a recommendation to the agency.

Once an application is submitted, “The FDA really looks very, very carefully at the data in each age group and in each demographic group,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said during a call on Friday.

After the meeting, FDA staff members consider the committee input along with the agency’s evaluation of the company’s data and will make a decision about whether the vaccine should by authorized.

Shortly after an EUA, the CDC’s Advisory Committee on Immunization Practices, also known as ACIP, goes through the data, too.

Once the CDC committee has made a recommendation and it has been approved by the CDC director, the company plans to ship the vaccines immediately and it can go into arms right away.

How long does the authorization process take?

The process for the Johnson & Johnson vaccine should be about the same as it was for the Moderna and Pfizer vaccines, according Offit, who is a member of the FDA’s VRBPAC.

With the Pfizer vaccine, it took a little over three weeks from the time the company submitted its data to an EUA. With the Moderna vaccine, it took a little more than two weeks.

If the vaccine is authorized for emergency use, “our plan is to have supply immediately upon launch,” Mammen said.

How many doses are there?

The US has ordered 100 million doses and the company has been manufacturing it while it has been testing the vaccine. Typically, companies wait to make the vaccine after its been approved, but that changed during the pandemic.

Johnson & Johnson says it can meet its 100 million dose commitment by June.

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