How the COVID-19 vaccine from Johnson and Johnson works

Vaccine uses a "viral vector" approach
Viral vector vaccine from Johnson & Johnson
Posted at 7:18 PM, Jan 19, 2021
and last updated 2021-01-21 08:55:47-05

SAN DIEGO (KGTV) -- The Food and Drug Administration has informed members of its vaccine advisory committee to be ready for a possible February meeting date to consider a COVID-19 candidate, likely the vaccine from Johnson and Johnson, according to a committee member.

The exact date will depend on when the company finishes analyzing data from its Phase 3 clinical trial and submits an application, said advisory committee member Dr. Mark Sawyer of Rady Children’s Hospital.

On Sunday, Dr. Anthony Fauci, the nation’s top infectious disease doctor, said FDA consideration of another vaccine candidate was “weeks, not months” away.

Like the vaccine candidate from AstraZeneca and Oxford University, the Johnson and Johnson vaccine uses viral vector technology. Scientists have been experimenting with viral vectors since the 1970s.

“There’s a vaccine developed for Zika using this technology, for Ebola using this technology, for HIV using this technology. Now none of those have been widely used, but we’re pretty familiar with the technology and pretty comfortable about how it works,” Dr. Sawyer said.

In this approach, scientists take genetic code from the coronavirus’ spike protein and insert it into a harmless virus that acts as a transport vehicle.

“It’s like a spaceship,” said Dr. Peter Chin-Hong, an infectious disease specialist at UC San Francisco. “It brings the genetic code to the cell and then the cell sees the genetic and all of a sudden starts making the spike proteins.”

Those mock spike proteins produced by the body’s cells won’t make you sick (nor will the inactivated viral “spaceship”), but they’re enough to familiarize your immune system and jumpstart the production of antibodies and other defensive cells.

The vaccines produced by Pfizer and Moderna also trigger the body’s cells to create a mock spike protein, but they do it differently: using mRNA wrapped in tiny bubbles of fat.

Those tiny bubbles of fat and the single-strand mRNA are fragile. The mRNA vaccines have to be kept at cold temperatures to keep them intact, requiring a cold chain of distribution that adds a layer of complexity. But the J & J approach, with double-stranded DNA in a viral shell, is more robust, allowing for storage in a standard refrigerator for up to three months.

There have been a handful of reports of severe allergic reactions to the mRNA vaccines. Doctors suspect they may have been caused by a reaction to oily lipid bubbles.

“Adenovirus vectors, you don’t have to deal with any bubble,” Dr. Chin-Hong said. “So we wouldn’t and shouldn’t expect any of these kinds of severe allergic reactions.”

J & J is testing its vaccine as a single dose, unlike the two-dose vaccines from Pfizer, Moderna and AstraZeneca. The final results of the Phase 3 clinical trial will determine if J & J’s vaccine can be successful as a single dose or if it will also require two doses, Dr. Sawyer said.

Last week, the company revealed data from the first two phases of its clinical trials showing 90 percent of vaccinated volunteers produced potent neutralizing antibodies within 29 days. It’s an encouraging sign but not conclusive evidence of the vaccine’s efficacy, Dr. Sawyer said.

“I’m looking forward to the big Phase 3 clinical trial results to see if that one dose is really up there in the 70, 80, 90 percent effectiveness range,” he said.