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Why data around 'breakthrough' cases can show the vaccine works

Posted at 6:44 AM, May 06, 2021
and last updated 2021-05-06 06:44:41-04

Sheri Houghland was one of the first in the state to get vaccinated. As a healthcare worker, she was able to get the shot back in November. It was a relief after months of pandemic-related stress. And for five months things went as she anticipated: she was COVID free.

That changed two weeks ago when she tested positive.

"I broke the CDC rules and got a little overly confident and ended up spending some time with a friend who was unvaccinated indoors, without masks," said Houghland.

After spending two days visiting a friend on the west side of the state, Sheri went back to Detroit only to receive a phone call: her friend had a fever. While Sheri had felt a bit under the weather, she had attributed the fatigue to traveling.

"Maybe this is not COVID, maybe this is just a flu; I’m vaccinated," she remembers thinking. But she also knew there was a chance that she had COVID, especially after spending time indoors with someone who hadn't been vaccinated. And so she went to get tested.

"It was positive," she said. "So, yeah, that was just two weeks ago."

Sheri is what the medical community calls a “breakthrough” case: Vaccinated people who test positive 14 days or more after being fully vaccinated. According to the State of Michigan, less than 1% of those vaccinated -- 2,108 people — have met this criteria.

"I was irresponsible, and I kind of knew that going in," said Houghland. "I was taking a risk. Like we said, the vaccine is 95% effective."

While breakthrough cases serve as a reminder that vaccines don’t make people invincible to the virus and that precautions should still be taken, they also demonstrate the ways the vaccine is working, by stopping people from getting severely ill.

"There’s a lot of concern about what about these breakthrough cases, and I can tell you, we’ve seen a few breakthrough cases at the hospital, but they’re still a small minority," said Dr. Leonard Johnson an infectious disease specialist at Ascension Michigan. "The majority of people we’re seeing are people who are unvaccinated, or only received one dose and have not completed the series yet."

Health systems in the state are currently reporting breakthrough cases to the CDC. But many of the hospitalized breakthrough cases are discovered almost accidentally.

"On the hospital side, it’s still a rare thing," said Dr. Hanady Daas, an infectious disease specialist at Beaumont Health. "And to be honest with you most of those cases are usually incidental findings. They were the victim of an accident or an injury and they had to undergo surgery so they had a COVID test that showed up to be positive but they had no symptoms."

According to the Michigan Department of Health and Human Services, only 41 of the state’s breakthrough cases resulted in hospitalizations. While 22 resulted in death; its a fatality rate of 0.00069%. The COVID fatality rate in Michigan is, on the other hand, 3%. It spikes to 16% for those 70 and older.

"There is a contrast," said Daas, "between what I used to see and those kinds of patients who have comorbidities or are immunocompromised before the era of vaccination and the patients with COVID in the era of vaccinations."

In recent months the CDC has updated its guidance for vaccinated individuals. Currently, vaccinated people can meet indoors, without masks, with up to ten other fully vaccinated people. They are also not required to wear masks outdoors except when attending crowded outdoor activities like concerts, parades, and sports events.