HARRISBURG, Pa. (WHTM) — The nation’s coronavirus cases have nearly tripled in the last two weeks and some full-vaccinated Americans are still getting the virus, but not getting nearly as sick.

“We have patients that are vaccinated and then they get COVID and these are what we call, “breakthrough” cases,” Dr. Mark Goedecker, Vice President and Chief Medical Officer for Primary Care at WellSpan Health said.

The Delta variant is the main culprit because not only does it make up most of the country’s cases, but it’s more infectious.

“What happens with the delta variant is that when you get infected with it, you produce a lot more virus than what we call the alpha variant,” Goedecker said. “If I had it and I’m not vaccinated and I have lots of that virus and I sneeze or cough, and there’s someone near me, then they’re going to get infected with that.”

The vaccine isn’t always a perfect shield and sometimes, the virus can get through. When that happens, the body’s immune system and the vaccine, kick in.

“If you’ve been vaccinated, what will happen is that those antibodies you have will go and attack the virus and kill it and prevent it from replicating,” Goedecker said.

People who are unvaccinated account for most of the COVID hospitalizations.

“We know that our older patients have higher vaccination rates so we are seeing more younger patients that are not vaccinated that are getting sick but also getting more severe disease and getting hospitalized,” Goedecker said.