What You Need to Know About the Johnson & Johnson COVID-19 Vaccine

What You Need to Know About the Johnson & Johnson COVID-19 Vaccine

We have a new tool in the fight against COVID-19. Here’s how the shot works and what you can expect if you get it

COVID-19 Vaccine

And then there were three: A COVID-19 vaccine developed by the Janssen Pharmaceutical Companies of Johnson & Johnson is now the third coronavirus vaccine available and authorized for emergency use by the U.S. Food and Drug Administration (FDA). Unlike the Moderna and Pfizer/BioNTech shots, you only need one dose of the Johnson & Johnson vaccine. And because it stays stable in a normal refrigerator for at least three months, it will be simpler to ship it to rural communities and easier to administer it in regular doctor’s offices that may not have access to specialized equipment.

Is this new vaccine as effective as Moderna’s and Pfizer/BioNTech’s? How exactly does it work, and what are the side effects? Here’s what you need to know, and why experts think you should take it if it’s offered.


How Does the J&J Vaccine Work?
This vaccine is what’s known in the science world as an adenoviral vector vaccine, making it different than the mRNA vaccines that were approved late last year. It’s also different than the conventional vaccines you’re familiar with, like those for the flu or pneumonia. A flu shot, for example, uses dead or weakened influenza germs to stimulate an immune-system response in the body.

The J&J vaccine uses a modified and harmless adenovirus to deliver the instructions that will help your body learn to fight off SARS-CoV-2, the virus that causes COVID-19. Normally, adenoviruses cause the common cold, but scientists have altered this one so that it can’t replicate and make you sick. Here’s the breakdown:  

  1. The adenovirus contains the gene (the blueprint) for producing the coronavirus’s spike protein.
  2. When you get the shot, the adenovirus connects with your cells and delivers the instructions.
  3. Your cells then start producing the spike protein, which primes your body’s immune system to start building its defenses against the real thing.
  4. Neither the vaccine nor the spike protein your cells produce contain the actual coronavirus, and they can’t make you ill.

While Johnson & Johnson’s vaccine technology is different than that of Pfizer and Moderna, it’s not new. The company used similar technology to create its Ebola vaccine (which was approved in July 2020), and in investigational vaccines for HIV and Zika.

Want to learn more about who is eligible or find where to schedule an appointment?

or call the Arkansas Department of Health at 1-800-803-7847.

How Effective Is the New Vaccine?
Research shows that 85% of people were protected against severe forms of COVID-19, and no one died or was hospitalized 28 days after vaccination, according to trial data that included 39,321 adults in the United States, Latin America, and South Africa.


When it comes to preventing more moderate illness, the vaccine showed about 66% efficacy worldwide. In the United States, the number who avoided moderate to severe symptoms was slightly higher: 72%.

According to researchers, the protection offered by the Johnson & Johnson vaccine was generally consistent across race, age groups, those with comorbidities, and multiple virus variants, including protecting against severe cases of what’s believed to be a more contagious strain that originated in South Africa.

It may appear that the Johnson & Johnson vaccine isn’t as effective as Moderna’s and Pfizer/BioNTech’s (which are approximately 94% effective at preventing symptomatic COVID-19 infections). But experts say it’s more complicated than simply comparing the numbers. For one thing, the clinical trials for the three vaccines weren’t designed exactly the same way, explains Robert H. Hopkins, M.D., a professor of internal medicine at the University of Arkansas for Medical Sciences and chair of the National Vaccine Advisory Committee. Plus, the Johnson & Johnson trial took place at a different time than Pfizer’s and Moderna’s. Infections were more widespread, there were more variants, and there were higher rates of hospitalization. “I think these factors make it difficult to compare the vaccines,” Dr. Hopkins notes.

The most important thing to remember is that all of the vaccines so far offer complete protection against hospitalization and death.

Does the J&J Vaccine Have Side Effects?
It’s described as “generally well-tolerated” in a Johnson & Johnson report, and the side effects were mostly mild to moderate and resolved in one to two days. The most common were pain at the injection site, headache, fatigue, and muscle pain—typical side effects from getting a vaccine. And there were very few reports of serious allergic reactions.

Can You Choose Which Vaccine You Get?
At this point, no. “We don’t have enough vaccine available to do that,” says Dr. Hopkins. Rather, your state’s health department or agency administering the vaccine will make the decision, likely based on which vaccine is available in a specific area or setting. “As more vaccines become available, there may come a time when we can say vaccine A is better for this group and B is preferred for this group—but we’re not there yet,” explains Dr. Hopkins.

His advice: “If you have the chance to get a vaccine, get it. Take what you are given. It’s still going to be a heck of a lot better than anything else you can do to protect yourself from getting severely ill.”

The information in this story is accurate as of press time and posting. To limit the spread of the coronavirus, it’s important to continue practicing social distancing (keeping at least 6 feet away from people outside your household) and washing your hands frequently. You should also be appropriately masked any time you’ll be in public. According to the CDC’s latest guidance means layering a disposable surgical mask underneath a snug-fitting cloth mask or placing a mask fitter over your cloth mask to ensure a tight fit. Because the situation surrounding COVID-19 continues to evolve, we encourage readers to follow the news and recommendations for their own communities by using the resources from the CDCWHO, and their local public health department.

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