FACT vs. FICTION: What’s driving the spike in breakthrough COVID cases?

PITTSBURGH — We took a closer look at the data, and we are seeing a trend of increasing breakthrough cases among vaccinated people.

In Allegheny County, for October and November, breakthrough cases made up about 38-percent of all COVID cases. We learned that was 15-percent more than the previous month, September, which had about 23-percent breakthrough cases.

So, why so many now? Should we be alarmed by the increase?

We asked University of Pittsburgh infectious disease expert Dr. Lee Harrison.

“No, it’s not alarming at all. Actually, the vaccines are working really, really well. They work best against severe infection. So really, really good at keeping you out of the hospital and from dying, but less effective in terms of mild disease,” Dr. Harrison said.

Breakthrough Hospitalizations & Deaths

While Dr. Harrison says vaccines are still highly effective against severe illness for most people, we do see some hospitalizations and deaths among break-through cases.

We requested recent numbers from the Pennsylvania Department of Health, which hadn’t been published yet.

We learned, for September and October, about 25-percent of hospitalizations statewide were breakthrough cases; and for August, the most recent month available, 25-percent of COVID deaths in Pennsylvania were breakthrough cases.

Dr. Harrison says those deaths are primarily among people who have serious underlying conditions.

“There are some deaths. A relatively small proportion of deaths are among the immunized, and those tend to be among the really debilitated, the elderly, and some people who have underlying conditions that predispose to not responding well to the vaccine,” he explained.

Why so many breakthrough cases?

So, what exactly is driving the increase in breakthrough cases? Dr. Harrison says there are several factors.

First, he points out that proportionately there are just more vaccinated people at this point. Right now, it’s estimated 65-percent of the population in Allegheny County is fully immunized versus only 35-percent who are unvaccinated.

So, the pool of individuals who can get breakthrough cases is bigger, even with a vaccine shown to be more than 90-percent effective against severe cases.

“We expect to see breakthrough cases when there’s so much virus circulating and when so many people are immunized,” Dr. Harrison said. “But again, the vaccines are working very well and protect you against severe COVID and even milder COVID; it’s just that we do see breakthrough cases,” he said.

Another factor leading to more breakthrough cases is the more contagious Delta variant.

“We’ve had a real invasion of the community with delta. And with Delta, the vaccine still works really, really well against severe disease, but somewhat less well against milder disease. So, that’s accounting for some of the increase, as well,” he explained.

Breakthrough Case Symptoms

If you get a breakthrough case, the top five symptoms are:

  • Headache
  • Sneezing/Runny nose
  • Muscle aches and pains
  • Sore throat
  • Loss of smell

But those symptoms tend to be milder in breakthrough cases and clear up more quickly-- making you less contagious to others.

“What we’re seeing is that the antibodies in your blood are basically controlling that infection much more quickly. And so, the infectiousness goes way, way down if you’re vaccinated,” Dr. Harrison said.

Protecting Yourself during the Holidays

As we head into the holidays, Dr. Harrison says he does expect to see a spike in COVID cases.

So, how can you best protect yourself?

“My recommendation is get vaccinated, get boosted if you’re eligible, and wear a mask and socially distance when you can, particularly indoors,” he said.

He acknowledges that people are becoming COVID weary but says there’s not much we can do about it.

“I’m tired of it, too, but COVID is not tired, at all. And so, we’re going to have to deal with it.”

Especially now, as we await more information on the new Omicron variant, it looks like there’s no end in sight to COVID precautions. And moving forward, Dr. Harrison anticipates booster shots will likely be needed every year, just like the flu shot.