BILLINGS — With over half of Yellowstone County residents vaccinated against COVID-19, you are urged to make sure you get a booster shot or third dose of the vaccine.

Booster shots and third doses have become a focal point, and it can be very confusing to understand which one you should be getting if you are eligible.

Dr. Erica Bruen, at St. Vincent Healthcare, says the vaccine is the same whether it's your first, second, or third dose, or the booster shot.

While the actual vaccine is the same, doctors do make a distinction between a booster shot and a third dose. The third dose is specifically for people who received the Moderna or Pfizer vaccine, and because of their compromised immune system, they may have not gotten the level of protection needed from the first two doses.

"People who are on medications that generally deplete their immune system. A lot of the time we think of people with autoimmune diseases, we think about people on chronic steroids, we think about people who are getting infusions or if they're on cancer treatments and they're on chemotherapy because their immune system is not going to respond to the first two shots like someone else," Dr. Bruen said.

The booster shot is only for people who got the Pfizer vaccine. Adults age 65 and older living in long-term care facilities and those age 18 and older with underlying or chronic medical issues should receive a booster six months after getting a second dose of the vaccine.

"And that's where you need to talk to your medical provider to see if you fall underneath that category, but a lot of people do fall underneath that category because that's talking about those who have obesity or health disease, or if they have COPD, or lung disease, or asthma. Those are all things we see causing more severe disease, so they would be at higher risk for more severe disease if they were to get a breakthrough infection," Dr. Bruen said.

The booster shot is also meant for people working in high-risk jobs, such as healthcare workers, teachers and grocery store clerks.

"We're seeing the immunity wane," Dr. Bruen said. "That's not unexpected, but we're seeing immunity wane down to a point where there's breakthrough infections. The fact that we're getting the booster shot doesn't mean that the vaccine was not good or that it didn't work."

The Pfizer booster shot is currently the only booster authorized by the Food and Drug Administration.

A booster dose of the Moderna and the Johnson & Johnson vaccines is expected to be approved within the coming months.