How Johnson & Johnson’s Covid-19 vaccine works
Here’s what’s known about how it works and how it will fit into the mix of vaccines.
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.
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.
How is it different from the other Covid-19 vaccines?
“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
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&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.
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.
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.
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.
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.
