J&J COVID-19 vaccine candidate protects monkeys after single dose

Rather than building its COVID-19 vaccine candidate with mRNA—the new technology that rivals Moderna and Pfizer have turned to—Johnson & Johnson selected an older vaccine platform that had proven to be safe in diseases like RSV and Ebola. Now, it’s reporting that a single dose of the vaccine protected nonhuman primates in a preclinical study.

Scientists led by Beth Israel Deaconess Medical Center in Boston tested seven different vaccine candidates from J&J's Janssen unit in 32 monkeys. Another 20 animals received placebo shots. The team said all of the vaccinated monkeys developed neutralizing antibodies against SARS-CoV-2, the virus that causes COVID-19, and six that received the optimal vaccine did not show the infection in their lungs after being exposed to the virus. The 20 animals that received the sham shots all got sick. The researchers reported the results (PDF) in the journal Nature.

J&J's leading vaccine candidate, Ad26.COV2.S, is now being tested in a phase 1/2a study in 1,000 volunteers in the U.S. and Belgium, the company said in a statement. It expects to start a phase 3 study in September.

Ad26.COV2.S delivers the SARS-CoV-2 spike protein into cells using an inactivated common cold virus as the delivery vehicle. That prompts the immune system to launch an attack against COVID-19. A Beth Israel team led by immunologist and Harvard medical professor Dan Barouch, M.D., Ph.D., worked with J&J to develop the seven vaccine candidates, each of which expressed a different variant of the spike protein.

Of the seven variations, Ad26.COV2.S generated the highest amount of neutralizing antibodies in the animals, and the antibody response seemed to correlate to protection against the virus, the researchers reported.

RELATED: Johnson & Johnson to start human testing of COVID-19 vaccine next week

Instead of using viral proteins to prompt an immune response, the leading mRNA vaccines deliver bits of COVID-19’s genetic information into cells, which then use it to produce the spike protein. The mRNA vaccines from Moderna and Pfizer are designed to spark immunity with two shots.

In J&J’s newest preclinical study, the animals got a single shot of the vaccine candidates, and that did provide significant immunity to COVID-19. But previous studies by Barouch’s group showed that giving a second booster shot raised the antibody response by tenfold in both animals and people.

“A single-shot immunization has practical and logistical advantages over a two-shot regimen for global deployment and pandemic control, but a two-shot vaccine will likely be more immunogenic, and thus both regimens are being evaluated in clinical trials,” Barouch said in a statement. J&J confirmed that all of the clinical trials of Ad26.COV2.S will evaluate both the one- and two-dose regimens.

Several COVID vaccine developers have released preclinical data this week. They include Moderna, which announced Tuesday that two doses of its candidate, mRNA-1273, protected nonhuman primates when they were exposed to the disease four weeks after the second dose. The regimen also produced an immune response similar to that seen in phase 1 human trials.

Inovio, meanwhile, said Thursday that its DNA vaccine against COVID-19 produced neutralizing antibodies and protective T cells in monkeys that persisted four months after the first of two doses. When the vaccinated monkeys were challenged with the disease, the responses from “memory” T and B cells quickly reduced the viral load and cleared it from the animals’ lungs and nasal passages, Inovio scientists reported in the journal preprint server bioRxiv.

Johnson & Johnson Chief Scientific Officer Paul Stoffels laid out the company’s vaccine development plan in a conference call earlier this month. The Belgium and U.S. trials will include an arm specifically for people 65 and older, he said, and trials in the Netherlands, Japan, Germany and Spain are also being planned.

If the company can generate sufficient data from the phase 3 trials by the end of the year, vaccinations could begin in early 2021, Stoffels said.

The Ebola vaccine that J&J developed using the same technology at the heart of Ad26.COV2.S was approved in Europe in early July. It’s used along with a shot from Bavarian Nordic. About 60,000 people have been vaccinated under that regimen.