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Johnson & Johnson one-shot vaccine appears to fare better against worrisome COVID-19 variants than first reported

New data are released in advance of a Friday advisory panel meeting on whether to recommend FDA approval.

Research assistant Zhenfeng Li prepared a test in the Barouch Laboratory, where they have been working with J&J to develop a vaccine for coronavirus at Beth Israel Deaconess Medical Center's Center for Virology and Vaccine Research in Boston, on March 5, 2020.Craig F. Walker/Globe Staff/file

Johnson & Johnson’s one-shot COVID-19 vaccine appears to provide more protection against worrisome virus variants than the drug giant initially reported, according to new trial data released before an advisory panel votes Friday on whether to recommend the vaccine as the third one cleared for emergency use in the United States.

Briefing documents posted on the Food and Drug Administration website Wednesday provide the most compelling evidence yet that the vaccine prevents serious illness despite the emergence of resistant variants. Those include variants that first surfaced in South Africa and Brazil and have since led to confirmed cases in the United States.


Overall, the vaccine that Johnson & Johnson developed with Beth Israel Deaconess Medical Center was 72 percent effective at preventing moderate to severe disease in the United States and 66 percent of such cases globally, according to the latest data. Across all regions, it was 85 percent effective at preventing severe illness and 100 percent effective at preventing coronavirus-related hospitalization and death.

The FDA signaled it was impressed with the vaccine, saying in a briefing document that Johnson & Johnson had provided enough manufacturing data to establish the product’s “quality and consistency for authorization.” The vaccine appeared to be safe and had milder side effects than the first two authorized vaccines, with no reports of severe allergic reactions like anaphylaxis, regulators said.

A panel of independent experts is scheduled to vote Friday on whether to recommend the FDA clear the vaccine. If, as expected, the panel gives its blessing, regulators could authorize the vaccine as early as Saturday and distribution could start within days. That would be welcome news, given the limited supply of the first two vaccines and their frustratingly slow and uneven rollout across the country.

When Johnson & Johnson announced interim results of its study on 43,783 participants on Jan. 29, it said the vaccine was 66 percent effective against the Brazilian variant and 57 percent effective against the South African variant. The pharmaceutical company tested the vaccine at multiple trial sites in both countries, where the variants cause most cases.


But the trial results improved over the past month as more data were analyzed. The vaccine is now 68 percent effective at preventing moderate to severe disease caused by the dominant variant in Brazil and 64 percent effective against the dominant variant in South Africa.

Although Johnson & Johnson’s trial results indicate robust protection overall, they fell short of the stellar performances of two-dose vaccines from Pfizer-BioNTech and Cambridge-based Moderna that were cleared for use in December.

Those vaccines prevented about 95 percent of coronavirus cases in large studies. But the trials were held before resistant variants emerged, and federal health officials and vaccine experts say the percentages would likely be lower if those studies were conducted now.

“We can talk about all the fine differences between these vaccines, but the most important message is that all of these vaccines are highly safe and highly effective, and all these vaccines are going to save lives,” said Dr. Dan Barouch, head of the Center for Virology and Vaccine Research at Beth Israel, which licensed vaccine technology to Johnson & Johnson.

Dr. Paul Offit, a pediatrician specializing in infectious diseases at Children’s Hospital of Philadelphia who sits on the independent panel of experts that will discuss Johnson & Johnson’s vaccine, said the “efficacy for preventing severe and critical cases appears to compare favorably” with the first two vaccines. But, he said, he wanted to hear from company officials and drug regulators Friday before forming an opinion.


Some 65 million doses of the Pfizer-BioNTech and Moderna vaccines had been administered as of Wednesday, according to the Centers for Disease Control and Prevention. The Johnson & Johnson vaccine would go twice as far as its rivals because it only requires one dose.

The briefing documents posted on the FDA website also provided a tantalizing early finding that could have major consequences if more evidence confirms it. A single shot of the Johnson & Johnson vaccine not only protected recipients against illness, it also appeared to prevent some asymptomatic infections, which many experts believe have fueled the epidemic.

Studies of several COVID-19 vaccines have suggested that inoculation may prevent infections that cause no symptoms but can spread to others, but experts say more research needs to be done. If vaccines do prevent asymptomatic cases, it might enable people to relax on mask-wearing and social distancing out of fear of spreading the virus.

Dr. Nahid Bhadelia, an associate professor at the BU School of Medicine who specializes in infectious diseases, said the Johnson & Johnson data is the latest good vaccine news this week.

On Monday, the FDA said it will quickly analyze booster shots against coronavirus variants and won’t require additional clinical trials for the new shots, a streamlined process similar to the one used for seasonal flu vaccines. On Tuesday, Pfizer and Moderna told Congress they expect to have provided the government with a total of 220 million vaccine doses by the end of March, up sharply from the roughly 75 million shipped so far. Now, Bhadelia said, a third vaccine could start getting distributed within days.


“The more people that we can cover with the blanket of immunity sooner — particularly the vulnerable — the better off we are,” she said.

When the Vaccines and Related Biological Products Advisory Committee meets Friday, Johnson & Johnson will almost certainly tout the data showing its vaccine has the highest proven efficacy against variants.

That was the view of several vaccine experts interviewed recently after the government of South Africa abandoned plans to use a rival vaccine developed by AstraZeneca and the University of Oxford. A small clinical trial in that country indicated that vaccine provided “minimal protection” against mild or moderate cases caused by the more contagious and resistant variant. Instead, South Africa has started administering the Johnson & Johnson vaccine to health care workers.

Dr. Nelson Michael, director of the Center for Infectious Diseases Research at Walter Reed Army Institute of Research, told the Globe he “would be stunned” if the events in South Africa do not come up during the advisory panel meeting.

Dr. Anthony Fauci, the nation’s top infectious disease expert, acknowledged last month that public health officials will likely face a “messaging challenge” to persuade people to take a vaccine that prevented 66 percent of symptomatic cases overall compared with roughly 95 percent. But he said the Pfizer and Moderna vaccines would likely get less impressive results now, given the emergence of resistant strains. The protection that the Johnson & Johnson vaccine provides against severe cases, he said, was a far more important measure.


Last summer Fauci said a COVID-19 vaccine would have to be at least 50 percent effective for the government to authorize it for emergency use. By comparison, the seasonal flu shot is typically 40 to 60 percent effective, according to the CDC.

Executives at Pfizer-BioNTech and Moderna have said that their vaccines should protect people from the South African variant, based on test tube studies showing that blood samples from vaccine recipients had enough antibodies to neutralize the variant.

Moderna acknowledged on Jan. 25 that the South African variant caused a sixfold decrease in disease-fighting antibodies generated by its vaccine. But the company said that level was likely still sufficient to provide immunity. Fauci agreed, saying the Pfizer-BioNTech and Moderna vaccines should have “enough cushion” in antibodies to work against the variant.

Nonetheless, Moderna said Wednesday that it is testing several potential booster shots against the South African variant. They include a version of its vaccine tailored to the viral mutant and a third shot of the authorized vaccine.

The federal government has a deal with Janssen Pharmaceuticals, a Johnson & Johnson subsidiary, worth about $1 billion for 100 million vaccine doses that Janssen has promised to deliver by the end of June. Because the vaccine can be administered in one shot, that would mean full coverage for 100 million people. The agreement gives the government the option to order an additional 200 million doses.

The company this week said it could deliver 20 million of the doses by the end of March.

In addition to the advantage of requiring one shot instead of two, the Johnson & Johnson vaccine is stable at normal refrigerated temperatures. The Pfizer and Moderna vaccines must be kept at frigid temperatures until being thawed before vaccination.

Like messenger RNA vaccines made by Pfizer-BioNTech and Moderna, Johnson & Johnson’s vaccine relies on a cutting-edge approach to stimulating immunity. It uses a harmless and relatively rare cold virus, adenovirus serotype 26 ― or Ad26 ― as a Trojan horse to deliver part of the distinctive spike protein on the coronavirus surface into cells to trigger an immune response without making people sick. Adenovirus-based vaccines have been investigated for about three decades but have yet to be licensed for use in the United States.

Jonathan Saltzman can be reached at