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Johnson & Johnson said Friday that its single-dose Covid-19 vaccine reduced rates of moderate and severe disease, but the shot appeared less effective in South Africa, where a new coronavirus variant has become common.

Overall, the vaccine was 66% effective at preventing moderate to severe disease 28 days after vaccination. But efficacy differed depending on geography. The shot was 72% effective among clinical trial volunteers in the U.S, but 66% among those in Latin America, and just 57% among those in South Africa. Though markedly below the levels seen with the first two authorized Covid-19 vaccines, those rates are above the thresholds originally set by the U.S. Food and Drug Administration for a vaccine to be considered useful.


The vaccine reduced severe disease alone by 85%, and prevented Covid-related hospitalization or death, Johnson & Johnson said.

“In a pandemic, if you can, with a single-dose vaccine, very quickly eliminate the severe consequences of death, hospitalization, and severe disease, that’s what’s important for society,” Paul Stoffels, the company’s chief scientific officer, told STAT.

Eric Topol, director and founder of the Scripps Research Translational Institute, called the results “disappointing,” but added that a vaccine that prevents the most serious outcomes, such as hospitalization and death, is still valuable. “It reinforces how lucky we were that the first two were more effective,” he added.


Anthony Fauci, the director of the National Institute for Allergy and Infectious Diseases, cautioned at a press conference against making too much of comparisons to prior vaccines, calling the result “extraordinarily important,” noting that severe disease was reduced across the board, even in regions where new variants of the virus were common.

“So this has really important domestic and global public health implications,” Fauci said, “things that we know about this particular candidate that even add to the importance globally, namely the minimal cold chain requirements, the inexpensive nature of it, the fact that it is one shot and that the company can actually produce in a reasonable period of time, billions of doses.”

The results set off a new phase in the battle against the SARS-CoV-2 virus, which causes Covid-19. Different vaccines against the virus are proving to have varying levels of efficacy, but also distinct attributes that could make them more — or less — valuable in certain contexts.

Results from the first two authorized vaccines, one from partners Pfizer and BioNtech and a second from Moderna, were considerably stronger, reducing symptomatic infection by about 95%. But those vaccines require two doses. They also come with distribution challenges since they are required to stay at ultra-cold temperatures.

The new variant of the virus that was first identified in South Africa, B.1.351, throws another monkey wrench into the equation. It appears to make vaccines less effective. Novavax, another vaccine manufacturer, said Thursday that its vaccine was 90% effective in the U.K. but just 49% effective in South Africa. The existence of such a variant raises the possibility that vaccine makers will have to develop booster shots to protect against it. They might even need to do so regularly, as new strains of the coronavirus emerge.

The efficacy of authorized vaccines appears to be somewhat lessened by the B.1.351 strain in test-tube experiments, but have not been put to the test against it yet in clinical research.

“The policy implications of having different vaccines with different levels of efficacy are huge,” said Carlos del Rio, a professor of infectious diseases at the Emory University School of Medicine. “To deal with this pandemic and stop the spread, I think you use all the tools in the toolbox.”

The J&J results are from an interim analysis of a study of 44,325 volunteers in which 468 symptomatic cases of Covid-19 occurred. They are being unveiled Friday morning at a press conference with the National Institutes of Health, which helped run the study as part of the U.S. vaccine effort, known as Operation Warp Speed. Because the study is still ongoing, the data could still change.

Unlike the Pfizer/BioNTech and Moderna vaccines, which are based on a new technology called mRNA that uses the body’s own cells to produce a key viral protein, the J&J vaccine uses a type of virus called an adenovirus to deliver genes that produce those same viral proteins. A similar technology was used in the vaccine developed by Oxford University and AstraZeneca.

J&J said that the trial did not result in any significant safety concerns about the vaccine. A case of stroke in one volunteer, which prompted researchers to pause the trial this fall, was determined to be unrelated to the vaccine, Stoffels said. Fevers occurred in 9% of those who received the vaccine, and fevers of more than 104 degrees occured in 0.2% of vaccine recipients. Serious adverse events were more common among those who received placebo than the vaccine.

No matter the age of volunteers in the study, the vaccine appeared to have strong efficacy, Stoffels said. There had been concerns its effectiveness might be less robust in older people.

Akiko Iwasaki, a virologist at Yale University, said that the results for both the Novavax and J&J vaccines were strong. She noted that it’s difficult to compare the J&J results to those from other trials, because the earlier trials counted cases of mild Covid-19 whereas the J&J study included only sicker ones.

Regardless, Iwasaki emphasized the importance of simply vaccinating as many people as possible, because the current lack of immunity in the majority of the population, and the high number of cases, is giving the virus an opportunity to mutate more often.

“We’ve got to get the first dose to as many people as possible,” Iwasaki said. “These variants that are more transmissible and potentially even more lethal are on the rise. I think time is really what we’re fighting against.”

Kert Viele, a statistician at Berry Consultants, made a similar point. Approving more vaccines, and expanding global supply, could mean communities reach herd immunity, in which enough people are inoculated against a pathogen to halt chains of transmission. “If we can lower global cases,” Viele said, “we will reduce the emergence rate of all of these strains to everyone’s benefit, and thus the need for such reformulations in the future.”

One hope is that the efficacy of the Johnson & Johnson vaccine could rise if it is given as a two-dose regimen. Johnson & Johnson is running another large study, enrolling 30,000 patients, testing two doses of the vaccine given 57 days apart. However, Stoffels said, waiting that long between doses will slow results. He expects results of the two-dose study to read out in the summer or fall.

The population in the study was “diverse and broad,” J&J said. Patients came from the U.S. (44%), Central and South America (41%) and South Africa (15%). Women made up 45% of the study, and men 55%. Among participants globally, 59% were white, 45% Hispanic or Latinx, 13% were Black, 6% were Asian and 1% were Native American. Volunteers had health conditions including obesity, type 2 diabetes, hypertension, and HIV.

The J&J vaccine will be far easier to distribute than the mRNA vaccines made by Moderna and Pfizer/BioNTech. The vaccine will remain stable for two years at -4 degree Fahrenheit, and will remain stable for up to three months if kept at between 36 degrees and 46 degrees Fahrenheit.

Johnson & Johnson expects to file with the FDA for an emergency use authorization in early February, and, assuming the vaccine is authorized, will have some product ready to ship immediately after getting a go-ahead. The company declined to give specifics on how much would be available, except to say it expects to make all of its 2021 supply commitments.

  • Does anyone know if different vaccines can be layered? Scenario: Let’s say the J&J vaccine is available to me first. Could I get that but, later, as it becomes available, get an mRNA vaccine double-dose for the higher efficacy?

  • “Novavax, another vaccine manufacturer, said Thursday that its vaccine was 90% effective in the U.K. but just 49% effective in South Africa.”

    This is either a terrible oversight on your part or deliberate misinformation. Either way it is very poor journalism.

    The vaccine was 60% effective against symptomatic disease caused by the South African variant amongst HIV negative participants. You know the people who comprise 99.5% of the global population!

  • Can we stop with the relentless pessimism?

    This is incredibly positive news. Read the actual news release (have added emphasis through capitalisation):

    “Prevention of severe disease; protection against COVID-related hospitalization and death

    The vaccine candidate was 85 percent effective in preventing severe disease across ALL regions studied, [i] 28 days after vaccination in all adults 18 years and older. Efficacy against severe disease increased over time with NO cases in vaccinated participants reported after day 49.

    The Janssen COVID-19 vaccine candidate demonstrated COMPLETE protection against COVID-related hospitalization and death, 28 days post-vaccination. There was a clear effect of the vaccine on COVID-19 cases requiring medical intervention (hospitalization, ICU admission, mechanical ventilation, extracorporeal membrane oxygenation (ECMO), with no reported cases among participants who had received the Janssen COVID-19 vaccine, 28 days post-vaccination.”

    1) Works to prevent severe disease just as effectively in South Africa as the U.S. 95% of cases in S.A. were the new variant so suggests the new variant has an advantage in initially replicating but the vaccine stops it progressing just as effectively as the non-variant;
    2) Gets better over time post vaccination. 100% effective against severe disease 49 days post vaccination;
    3) 100% effective against critical disease requiring hospitalisation and death.

    Approve it NOW. Roll it out NOW!


  • Since I have been shoved to the back of the line with Type 1 diabetes, this is the crap vaccine I will end up with. I have been waiting for a call from the local VA but nothing yet. With all of the elderly we have in Kansas, we’ll never get to Phase 3 or 4.

  • Then don’t take it! The flu shot only protects 40% and yet how many people run to get vaccinated against the seasonal Flu? Lots Because 66% is better than 0% . You should be Congratulating all the scientists who are offering different vaccines In such a short time. Pretty much short of a miracle . Try being a little grateful

  • WHY would I choose a COvid vaccination that is only 66% effective? Come one now all the money and time spent to only make a vaccination that’s not that effective? WHY? Suggest the J&J can do better. My life on the line and why would choose to take a chance with my life being 2/3rds effective against a deadly virus???

    • Then don’t take it! The flu shot only protects 40% and yet how many people run to get vaccinated against the seasonal Flu? Lots Because 66% is better than 0% . You should be Congratulating all the scientist Who are offering different vaccines In such a short. Of time you too short of a miracle . Try being a little grateful

    • Because J&J is doing it the traditional way. They got cold virus and attach part of covid19 virus to it. At least it does not penetrate you cell and ask your cell to create the bits and pieces of the spike.

      Long term unknown side effects will probably be less. Therefore in terms of unknown long term side effects, it is probably safer.

    • The vaccine has the lower success rate at preventing the disease but has a 100 percent success rate at preventing the disease from killing you or requiring hospitalization. It is 85% effective at preventing you from seeking medical care. Read the article.

    • Hello,
      Does the J&J vaccine contain the chemical Polyethylene Glycol (PEG) that has been linked to so many post injection allergic reactions and complications in both the Pfzier and Moderna vaccines?
      I’m hoping not.
      Thank you!

    • We should be able to ramp up the production and distribution of the MRNA vaccines that are 90% (or higher) effective. I agree, 66% effectiveness for J&J is not that great. I suppose if we cannot get Pfizer and Moderna moving fast enough, it is better than nothing. This doesn’t make sense to me. Fauchi’s recent recommendation was to stick with the two vaccines we started with, Moderna and Pfizer. Making a booster for the more virulent and transmissable variants of Covid19 will supposedly be easier with the MRNA vaccines. Perhaps, Moderna and Pfizer are unable to ramp up the vaccine production? Even though these two vaccines require special handling we should be focusing on getting the more effective version out to people.

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