What You Should Know About Johnson & Johnson’s COVID-19 Vaccine

The third authorized vaccine provides protection, particularly against severe illness and death, with just one shot.

Johnson & Johnson COVID-19 vaccine

Photo by PHILL MAGAKOE/AFP via Getty Images

The FDA has granted emergency use authorization for a unique single-shot COVID-19 vaccine produced by Janssen Pharmaceuticals, part of the drug company Johnson & Johnson (J&J). That means that there are now three vaccines authorized in the United States to help protect us against COVID-19.

For the immediate future, it’s unlikely that people will get to choose which COVID-19 vaccine they get, says Dr. Jason Zucker, an infectious disease specialist at NewYork-Presbyterian/Columbia University Irving Medical Center and instructor in medicine at Columbia University Vagelos College of Physicians and Surgeons. Here’s what you should know if you are offered the newest vaccine, which was authorized for adults 18 and over and provides protection against COVID-19, especially protection against severe illness and death.

1. U.S. studies found the J&J vaccine to be more than 70% effective.
Overall, the vaccine has a reported 66% efficacy rate in preventing moderate to severe disease from COVID-19, but in the U.S., the J&J vaccine had 72% efficacy. While this efficacy rate is lower than for the Moderna and Pfizer-BioNTech vaccines, which are around 95% effective, scientists believe this might be because the J&J vaccine was tested later than the Moderna and Pfizer vaccines. Therefore, there were more variant strains circulating when the J&J vaccine was tested than when the two other vaccines were tested, says Dr. Zucker.

The vaccine is still quite effective. “When the FDA first set out requirements for vaccination, 50% was determined to be acceptable. It certainly beats that. The bar has been raised by the mRNA vaccines,” he says, referring to the first two vaccines authorized in the U.S. “At the same time, we’re not able to produce enough vaccine for everybody in the world, so there’s a benefit in having a vaccine that works well above the threshold we initially set and get more people vaccinated quicker.”

2. The J&J vaccine provides significant protection against severe illness and death.
In global trials, the J&J vaccine showed an 85% efficacy rate in preventing severe disease. Among the people who received the vaccine, after 28 days no one who contracted COVID-19 was hospitalized.

“The J&J vaccine offered complete protection against COVID-19-related hospitalization and death,” says Dr. Zucker. “Nobody in the vaccine group died. That is ultimately the outcome we care about the most.”


“The J&J vaccine offered complete protection against COVID-19-related hospitalization and death.”

— Dr. Jason Zucker


3. You only need one shot of the J&J vaccine.
This is a big advantage over other available vaccines. A vaccine delivered in a single dose will allow more people to get vaccinated.

Nevertheless, a J&J clinical trial is underway to see if a second shot could boost the vaccine’s effectiveness, so the one-shot strategy could change, says Dr. Zucker. But one dose is still highly effective.

4. It uses a different technology from the first two vaccines approved in the U.S.
Unlike the Pfizer and Moderna vaccines, which are mRNA vaccines, J&J’s is a viral vector vaccine. This means that the vaccine is delivered via an adenovirus, a type of virus that normally causes colds.

The adenovirus is engineered to include a snippet of SARS-CoV-2-DNA, which encodes the spike protein – the part of the coronavirus that latches onto cells. This snippet is then sent to your cells to produce mRNA, which tells your cells to make copies of the spike protein. Like the mRNA vaccines, this prompts an immune response.

“Your immune system recognizes the spike protein as abnormal and develops antibodies against it,” says Dr. Zucker. It takes about 28 days to get the J&J vaccine’s full protection.

5. The new vaccine can be stored at refrigerator temperatures for a long period.
“One of the big advantages of the J&J vaccine is that because it has an adenovirus vector and double-stranded DNA as opposed to mRNA, it’s much more stable,” says Dr. Zucker.

As a result, the vaccine is much less temperature-sensitive. It can be kept in a refrigerator for up to three months, which should make it easier to vaccinate people in rural or underserved areas.

The mRNA vaccines have stricter requirements regarding cold temperatures. That’s because mRNA is extremely fragile and disintegrates rapidly when it’s too warm.

6. You should get whichever vaccine you are offered.
The J&J vaccine is safe and very effective, and will likely keep you from becoming severely sick if you do contract COVID-19, says Dr. Zucker.

“We still have a problem in this country with high rates of infection,” he says. “The best approach is to take the vaccine that you can get the easiest and as quickly as possible. It will protect you.”