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The new vaccine requires only one shot.

Millions of people have received the coronavirus disease 2019 (COVID-19) vaccines made by Moderna and Pfizer. Yet, most Americans are still waiting to get a vaccine. Fortunately, more vaccines are on the way.

The U.S. Food and Drug Administration granted emergency use authorization for the Johnson & Johnson COVID-19 vaccine on Feb. 27, 2021. This means we now have a third option.

You may be wondering about the differences between the vaccines and which one is best for you. Here are six things we know about the Johnson & Johnson vaccine.

1. It teaches your immune system to recognize and destroy the coronavirus.

Different vaccines work in slightly different ways. The Johnson & Johnson shot uses a weakened common cold virus, called an adenovirus, as a vehicle to deliver a single coronavirus gene into human cells. That gene then provides the instructions for making the SARS-CoV-2 spike protein. When the body makes the spike protein, the immune system reacts by making antibodies. Later, if exposed to COVID-19, the immune system remembers what the spikes look like and how to destroy them.

It’s important to know: The adenovirus has been genetically modified so that it cannot duplicate. It cannot give you a cold or COVID-19.

“The Johnson and Johnson vaccine uses a vector to get the information into the person being vaccinated so the immune system will recognize it and build an immune response in order to protect that person,” says UNC Health Chief of Infectious Diseases Joseph J. Eron Jr., MD.  “It’s a little different than the current Pfizer and Moderna vaccines, but it’s the same kind of idea: it gets that message inside the body so that the body can see it and respond.”

2. It’s a one-dose vaccine.

The Johnson & Johnson vaccine requires only one shot.

Only needing one dose could make a difference in getting as many people vaccinated as possible, Dr. Eron says. “It’s easier to only have to do it one time.”

This vaccine is also easier to store and ship because it does not require super-cold storage like the current vaccines. This means the vaccine can be used in more rural areas or areas that may not have a place to store them, Dr. Eron says.

3. It is 85% effective in preventing severe disease.

Like the other COVID-19 vaccines currently in use, the Johnson & Johnson vaccine will help prevent COVID-19. In clinical trials, it was 85 percent effective in preventing severe disease and essentially 100 percent effective in preventing hospitalization and death. In fact, when it comes to these most serious cases, the Johnson & Johnson vaccine “was very, very similar to the Moderna and Pfizer vaccines in protecting people from serious illness,” Dr. Eron says.

4. It is more effective against some COVID-19 variants than others.

Viruses are constantly changing, creating new versions—called variants.

“The virus’ job is to infect as many people as possible. It changes over time, so it can still spread, and that’s what we worry about,” Dr. Eron says.

Variants from Britain and South Africa have are different from what we have seen before. For example, the British variant appears to spread more easily. Researchers are working to understand whether serious COVID-19 disease is more common with these variants.

“As best we can tell, the Johnson & Johnson vaccine protects as well from the variant that’s appeared in England as it does for the most common variant in the United States,” Dr. Eron says.

The Johnson & Johnson vaccine was 66 percent overall effective in preventing people becoming sick with COVID-19 including new variants from Brazil and South Africa.

5. The new vaccine is now available in the United States.

Johnson and Johnson received emergency authorization use for its vaccine in the United States. Before the FDA authorizes this, it reanalyzes the clinical trial data.

“FDA scientists and statisticians review the data and see if they can reproduce the results using the data from the company. It’s a very rigorous assessment,” Dr. Eron says. “It may be a little bit slower, but it gives me comfort about the safety of a vaccine.”

6. If you’re eligible for a vaccine now, you shouldn’t wait.

When the vaccine becomes available in the United States, it means it has been through every stage of clinical trials that would normally take place for a vaccine. It is very important to understand that it is not possible to get a vaccine into humans without taking all the necessary steps.

“Millions of people have been vaccinated and we’re getting a very good sense of in the safety of these vaccines,” Dr. Eron says. “Getting vaccinated sooner rather than later is better. It’s so important to be vaccinated to protect yourself. We believe that if enough people get the vaccine, there’ll be less infection in the community. When this happens, it will be better for everyone.”

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