Health expert: Breakthrough COVID-19 cases were expected, and don’t mean vaccines are ineffective

In Mississippi, breakthrough cases make up approximately 10 percent of new cases over the last week
Published: Jul. 26, 2021 at 9:02 PM CDT|Updated: Jul. 26, 2021 at 9:14 PM CDT
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JACKSON, Miss. (WLBT) -In hospitals across the state, roughly one in ten people hospitalized with COVID-19 had been vaccinated, a statistic that may lead some to believe the vaccine doesn’t work, though health experts stress the opposite is actually true.

For 10 percent of those hospitalized to have been vaccinated, it means the overwhelming majority of cases — 90 percent — were not.

“The breakthrough cases are fully expected, have always been expected,” said Dr. Mark Horne, who also serves as president of the state’s medical association. “[We] always knew what was going to happen.”

Horne said the math behind the breakthrough cases is straightforward: if a vaccine is 95 percent effective, that means 5 out of every hundred who are fully vaccinated will still get the virus if exposed.

With the Delta variant, the efficacy of Moderna and Pfizer has been reduced slightly, with the most recent data suggesting closer to 88 percent effectiveness.

While some may wonder why a vaccine isn’t a hundred percent effective, Horne said that’s an impossible benchmark to achieve.

“People might say, ‘Well, why is the vaccine not perfect?’ Well, a couple of basic things. There’s never been a perfect vaccine ever,” Horne said. “There just isn’t. And expecting perfection is an irrational expectation. Two, people are different. And so, some people have more robust immune systems and a more robust response.”

Horne used the seasonal flu vaccine as an example, pointing out that, in a good year, that vaccine is 50 to 60 percent effective.

Why does a smaller fraction get infected anyway?

“These breakthrough cases are more often, not always, but more often in people who have a lesser immune response,” Horne said. “Perhaps they are on medications that suppress their immune response. Perhaps they have a chronic illness that suppresses their immune response. Perhaps they’ve been had cancer and chemotherapy.”

Health experts stress that even though there’s a chance you’ll still get COVID-19 even after your vaccination, your chances of developing severe symptoms and complications are drastically lower, as illustrated by the numbers seen in hospitals around Mississippi.

“I think we’re seeing people focus on the breakthrough cases and magnify the breakthrough cases. And what we really need to do is look at the overall positivity rates, who was positive that wasn’t vaccinated, who was positive that was vaccinated,” Horne said. “And you’re gonna see these dramatic numbers favoring vaccination as opposed to non-vaccination. This Delta surge is a surge in the unvaccinated population. The vaccinated population is doing vastly better.”

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