The Johnson & Johnson coronavirus vaccine is effective against the highly contagious Delta variant, even eight months after inoculation, the company reported on Thursday — a finding that should reassure the 11 million Americans who have gotten the shot.
The vaccine showed a small drop in potency against the variant, compared with its effectiveness against the original virus, the company said. But the vaccine was more effective against the Delta variant than the Beta variant, first identified in South Africa — the pattern also seen with mRNA vaccines.
Antibodies stimulated by the vaccine grow in strength over time, researchers also reported.
The results were described in a news release, and the company said that both studies had been submitted for online publication on Thursday. One of those studies has been accepted for publication in a scientific journal. Both studies are small, and the researchers said they had released the results early because of intense interest from the public.
“The coverage of the variants is going to be better than what people anticipated,” said Dr. Dan Barouch, a virologist at Beth Israel Deaconess Medical Center in Boston. “There was a lot of misinformation that was spreading, so we decided that we needed to get this into the public domain right away.”
The intense discourse about Delta’s threat has left even people who are immunized feeling anxious about whether they are protected. The variant, first identified in India, is much more transmissible than earlier versions of the virus, and its global spread has prompted new health restrictions from Ireland to Malaysia.
In the United States, the variant now accounts for one in four new infections. Public health officials have said the vaccines authorized in the United States work against all existing variants, but the data are mostly based on studies of the mRNA vaccines made by Pfizer-BioNTech and Moderna.
That left some people who received the Johnson & Johnson vaccine asking, What about us?
The frustration was building even before the Delta variant emerged. The Centers for Disease Control and Prevention’s guidance that vaccinated people could forgo masks indoors in many situations, for instance, was based mostly on data for mRNA vaccines. And reports of a cluster of infections among players on the Yankees baseball team who had received the J.&J. shot did nothing to assuage fears that the vaccine might be inferior to others.
Martha Young, 64, of Mountain View, Calif., received the J.&J. shot on April 9. It was not her first choice, but it was what was being offered. But since then, she said, “I’ve been very, very frustrated by the lack of information.”
She added, referring to the J.&J. vaccine, “I felt like I didn’t count, like I was statistically insignificant because so few of us have the shot that they didn’t have to worry about us.”
Some people who were immunized with the J.&J. vaccine complained that they felt cheated by experts who had said the vaccines were all equally good. “I was surprised to see others making this claim,” said Natalie Dean, a biostatistician at the University of Florida. “I didn’t like it. People don’t want to feel misled.”
But other experts said the clinical trials should have made it apparent that the efficacy of the J.&J. vaccine was lower than that of the mRNA vaccines. “Seventy-two percent is of course lower than 95 or 94 percent,” said Florian Krammer, an immunologist at the Icahn School of Medicine at Mount Sinai in New York.
Part of the difficulty in comparing the vaccines is that they were all tested individually and with different measures of success. The Pfizer-BioNTech and Moderna trials were designed to tally symptomatic infections, while the J.&J. trial assessed the vaccine’s prevention of moderate to severe infections.
Still, it’s clear that all the vaccines are much more effective at keeping people out of the intensive care unit and the morgue than scientists at first could have hoped, said Danny Altmann, an immunologist at Imperial College London.
“It’s like fighting over whether you want to have a Ferrari or a Porsche which goes 150 miles or 180 miles an hour in a street where you’re only allowed to go 30 miles an hour,” he said.
Still, there are differences: The J.&J. vaccine may permit more so-called breakthrough infections — which occur in people who are fully vaccinated — with mild to no symptoms than the mRNA vaccines do.
People with asymptomatic infections are highly unlikely to spread the virus, but their diagnosis can become a problem when routine testing picks them up — as in the case of the Yankees cluster — and they are required to go into quarantine, said John Moore, a virologist at Weill Cornell Medicine in New York.
Information about the effectiveness of the J.&J. vaccine has been slow to arrive, because it was rolled out later and because of the pause on its use following concerns about rare blood clots. Many medical centers and hospitals offered the mRNA vaccines early on to staff members and were able to set up studies assessing those vaccines.
But blood samples from people vaccinated with the J.&J. vaccine are a comparatively rare commodity, Dr. Krammer said. “It’s not that nobody cares, or it’s not we’re hiding something because the vaccine is not good,” he said. “It’s more of an access problem.”
In the absence of data, some experts had guessed that the J.&J. shot probably performed about as well against the Delta variant as the AstraZeneca vaccine, which is widely used in Europe. But that vaccine is given as two doses compared with J.&J.’s single dose.
“The thing that I’ve never completely understood about J.&J. is that their technology platform is essentially very, very similar — almost indistinguishable from AstraZeneca,” Dr. Altmann said. “Should it really be a two-dose vaccine like everything else?”
The single dose offers advantages for people with limited access or who do not want two doses for other reasons. The J.&J. vaccine also lasts longer than the others when refrigerated and was a welcome option earlier in the pandemic when vaccines were in short supply.
But after the emergence of variants like Beta and Delta that appear to partly sidestep the immune system, discussion about boosters for J.&J. recipients intensified. One dose of the AstraZeneca vaccine is much less effective against variants than two doses, and experts feared the J.&J. shot might be similar.
The new study addressed some of those concerns.
While blood antibody levels produced after immunization with Pfizer or Moderna drop after an initial surge, antibodies — and immune cells — stimulated by the J.&J. vaccine persist at high levels. (Other studies have shown that immune responses produced by mRNA vaccines are also likely to last for years.)
A dearth of information about the J.&J. vaccine had led many people to speculate that it might need to be supplemented with one dose of an mRNA vaccine. But at least for now, people who received the J.&J. vaccine should not need a booster, nor can they legally get one “unless they game the system, unless they pretend they’re vaccine-naïve and go and get an mRNA vaccine and essentially lie,” Dr. Moore said, “and I certainly don’t recommend people doing that.”