LANCASTER, Pa. (WHTM) — Breakthrough infections — which happen when vaccinated people test positive for COVID-19 — are becoming more and more common, and in Lancaster County, so are breakthrough hospitalizations.

This has some experts worried that vaccine immunity may be starting to wane.

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“The CDC was saying that at some point we would need a vaccine booster. What we’re waiting for is some solid data to tell us when,” Dr. Joseph Kontra, chief of infectious diseases at Penn Medicine Lancaster General Health, said.

Nearly 23% of COVID-19 patients at Lancaster General Health are vaccinated.

“It’s typical for what’s going on around the country, but if you look at the number of people in the ICU, that percentage is much lower.  If you look at the number of vaccinated people who actually die from COVID, that number is extremely small, and that gives you the benefit of the vaccine,” said Kontra.

But Kontra says this doesn’t point to a failure of science, just the reality that no vaccine is 100% effective.

“The alpha strain that was here over the wintertime saw very few breakthrough cases, and typically they were minimally symptomatic and not even requiring hospitalization, but the delta variant is clearly more contagious,” Kontra added. 

Kontra said the bottom line on vaccines is simple: “It’s much more effective at preventing severe disease, hospitalization, and death than it is at preventing infection in general, and that was the expected outcome of the vaccine from the beginning.”

Correction: In a previous version, we reported WellSpan had seen an increase in breakthrough cases. On the contrary, the percentage of unvaccinated patients has hovered around 90% for several months.