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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.

  • I believe that the results of the 2-shot regiment will be that this is much more effective. However, that will take time to find out. Americans may wind up skipping this vaccine, and it may be redirected to the least wealthy countries until the efficacy is higher. However, if supply is limited and the US numbers start creeping higher again due to the new variants, perhaps people will jump at something that will certainly keep you out of the hospital. The vaccine development has been nothing short of miraculous, and I don’t think that people are recognizing that. If anyone had said last April that next April, we would definitely have a vaccine that will keep everyone out of the hospital, we would have ben ecstatic (or told them that was wishful thinking).

    • As it stands, my locality is on a pace to vaccinate 60% of the population in about 350 days. Moderna/Pfizer will speed up a little– perhaps 10%– but it’s mostly J&J and AZ that provide an opportunity to accelerate that pace.

      For people in lower priority groups, a lower efficacy vaccine now instead of a better one in 300 days has got to be tempting. If you’re 45 with a couple comorbidities– or an essential worker but not “frontline”– you’re going to be waiting a long time but are still significantly exposed.

  • Should we be expecting Americans will say give me the less effective vaccine because I want my neighbors to get the more effective one? It ain’t going to happen. Anybody that knows anything about pharma would understand that a less effective medicine quickly becomes obsolete when a more effective medicine is available. Ask Merck about Shingles vaccine. Completely replaced by the GSK Shingles vaccine in a short period of time. Market it any way that you want but people will just wait for the “better” vaccine in most cases, especially if they are not in the High Risk Groups.

    • I would prefer to take this J and J vaccine far and away over either of the mRNA vaccines. The unknown risks involved with mRNA and the genetic component alone is more that enough to keep me waiting on a vaccine that would keep me out of the hospital with fewer questions regarding its long term risks.

  • I’m curious. Are clinical trial participants stratified by their personal habits? The infection rate would be higher among those who don’t wear masks or can’t avoid close contact with others. Conversely, the infection rate would be lower in people who are not exposed.

  • I don’t trust the people who made this so called vaccine what happened to people who are dying everyday behind aids? You guys can make a cure for the corona virus,but not for the people who are dying from aids everyday?

    • they have made a difference with aids people are living longer with a drug you need to look up facts before you write Image result for aids prevention pills
      Pre-exposure prophylaxis (or PrEP) is a way for people who do not have HIV but who are at very high risk of getting HIV to prevent HIV infection by taking a pill every day. The pill (brand name Truvada) contains two medicines (tenofovir and emtricitabine) that are used in combination with other medicines to treat HIV.

    • HIV/AIDS attacks the immune system directly and any vaccine against it needs counteract(and partially repair) the damage it can cause to your body’s defense against infection, including by the HIV virus itself.

      Complicating this is the fact that the HIV adapts to its victim’s immune system, many variants have appeared around the world that are specific to each region. Any vaccine would have to be formulated(by region) to target regional variants. The HIV virus globally is a “moving target” that is hard to “hit”.

      Experimental single dose HIV vaccines have shown almost zero efficacy, only combined multi-dose “layered”(different types of vaccines) experimental vaccine regimens have generated immune responses in trials against HIV. So any such regimen that can be proven to be at least 50% effective will be complex and not simple to distribute.

  • The headline is far too pessimistic. The key piece of data from the Ensemble trial: “85% Effective Overall in Preventing Severe Disease and Demonstrated Complete Protection Against COVID-19 related Hospitalization and Death as of Day 28.”

    Complete protection against hospitalization and death is what we care about. This is an enormous win. What’s more, the J&J trial was far more robust than the Moderna and Pfizer trials — you put Moderna/Pfizer against the new variants, their efficacy rates will drop as well.

    Unfortunately, the math-challenged in comment sections, like the NYT, are saying the J&J vaccine is bad, or they won’t take it. Dumb. Beyond dumb. The J&J vaccine prevents hospitalization and death after a month. Superb protection, gamechanger.

    • Except with zero vaccine the hospitalization rate is less than 15%. Basically it is going to be approved because the government guaranteed to pay for the vaccines whether effective or not

    • +1! I agree, the spin on this is disappointing. I don’t mind a week in bed with a fever if I can be protected from hospitalization and death. That’s what we need to get our society moving again. Give me that J&J!

    • I agree with you Jack – it’s a great win – and it’s effectiveness against hospitalization and death should really be the focus – it then actually does become “ just another flu”.

      Think of what the 2nd shot could achieve.

    • @Sean – that’s not how these calculations work. They split people into either a vaccinated and a non-vaccinated (placebo) group. Noone who received a vaccine was hospitalized. Nearly all (85%) of the people in the trial who had severe disease DID NOT receive a vaccine (i.e. were in the placebo group). So think about it this way. If you catch covid, your chances of becoming hospitalized go from 15% to 2.25%. Kind of a big deal.

    • @Joe — it’s better than that. Better than an 85% reduction was shown in hospitalization: *no one* was hospitalized or died in the vaccinated group. The 85% number is for reduction of ‘severe’ COVID.

      Of course, there’s a statistical margin of error– probably it isn’t quite 100% reduction in hospitalization, but it looks to be very good. (Looking forward to seeing the papers and understanding the credible intervals).

    • @Sean. I don’t think you understand what a 15% or 10% or even 5% hospitalization rate means for a contagious infectious disease.

      Even if you didn’t one would think you would have been listening to news. There are ~25 million cases in the United States 10% = 2.5 million hospitalizations. What is the average cost of hospitalization in the US? $5K? $10K? What of the cost of the patient time off work, the family members caring for the patient. The costs of counter measures so that others will not be infected (which is often futile?), what cost do you ascribe to the suffering.

      What is the cost of this vaccine? Like $10/dose?

    • They’re chasing the mutations now? Much like the flu shot; only good for one variant. Live on!

  • How do I get a Johnson & Johnson covid 19 vaccine?
    I am 70 with many medical conditions.
    I cannot get even an opportunity in New York City to register for a vaccine.
    Please help me.

    • If you live in a nursing home or other group care facility, you should get your vaccine there. If you do not live in a group care facility, you can make a vaccination appointment by:
      • Visiting to find a vaccination site near you
      • Calling 877-VAX-4NYC (877-829-4692) to make an appointment at a City-run site
      • Contacting your provider or pharmacy to see if they are offering vaccination

  • It might be as effective as the mRNA one with two shots. The decision to vaccinate more people, with lower effectiveness, is for the greater good.

  • I think this is an overly pessimistic view of the read out, and frankly, quoting Eric Topol (who has been an abysmal fear peddler on Twitter this entire time) is discouraging. If the vaccine offers an 85% reduction in severe disease, it’s very encouraging. We care about severe disease. Covid is likely to be endemic, just like other coronavirus that circulates. The only reason we care about it are severe outcomes.

    If there’s truly a concern about overall efficacy, then prioritize high-risk populations (65+) for the mRNA doses, while the broader population gets J&J. The single dose is an easier regimen, which probably would help encourage younger populations that may not be as concerned about Covid infection. And if Pfizer and Moderna end up being better in the long-run, the people that are most at risk for severe outcomes will be better protected from infection.

    • I would hardly call these results “disappointing”. 85% reduction in severe disease and 100% reduction in hospitalizations is incredible. People have to come to terms with the fact that this disease is here to stay at this point and will become endemic just like the flu and common cold.

    • Agree. The negative tone struck me as well. The article even reads like the vaccine eliminated 100% of hospitalizations and deaths, which if true, is the point. That should be the main take away. This is a fantastic outcome at this stage of the game because this is by far the most scalable product.

      Also one has to wonder whether the 2 dose vaccine regimens buy the higher efficacy with higher risk of adverse events, something yet unknown. So it is fantastic to have options. This vaccine also has a 2 dose study. The future results from that are the apples to apples comparison.

    • J&J should publish full data so that one could carefully look at complete hospitalization prevention and death.. how much sample size we have and in particular, can we say that for the SF variant as well.. if so.. that would indeed be a game changer.

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