SALT LAKE CITY, Utah (ABC4 News) –More Americans are receiving Pfizer’s booster shot, and new data from the Centers for Disease Control and Prevention finds no unexpected patterns of adverse reactions to the shot, which health experts say is good news.

A third jab to the arm is meant to boost immunity for those at high risk of contracting COVID-19.

“With the Delta variant being a lot more contagious, you have to have a vaccine that has a higher efficacy because of the way it spreads,” said Rich Lakin, the immunization director at the Utah Department of Health.

Pfizer’s coronavirus booster shot has been approved for people who are older than 65, over 18 and have a pre-existing condition, or have a job or living situation that poses a high risk of contracting COVID-19

While booster shots are being recommended to some, Dr. Sankar Swaminathan, the chief of the division of infectious diseases at the University of Utah Health, said it’s important for a person to know their risk of exposure and risk of infection.

“One is, how likely are you to get it at work or going about your daily life? And the second thing is, if you do get infected, how dangerous is it for you?” he said.

Dr. Swaminathan said with Utah’s high case counts, people are at greater risk of infection.

“Because there’s so much COVID in the community,” he said, “ a booster is probably more important than if you were in a low transmission situation.”

In new data from the CDC, some surveyed people who received an additional dose (at least six months after vaccination) report they experienced symptoms similar to what they felt after getting the second shot, which they said is pain at the injection site, fatigue, and a headache.

The CDC is studying the Moderna and Johnson and Johnson booster shots, and early data shows similar vaccine side effects to Pfizer. As of Wednesday, it’s not known when additional shots will be available.

“There’s no data that shows the importance of a booster shot for them right now,” Lakin said.

And he said people should not mix and match vaccines.

While the booster shot is being recommended to boost immunity, Lakin said being fully vaccinated is better than not.

“We stress that if you have not been vaccinated, you need to get your first one. If you’ve got your first one, get your second one,” he said.

Dr. Swaminathan also encourages Utahns to get the first and second dose, as he said that will decrease the risk of infection in the community.