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Why do COVID-19 breakthrough cases occur?

Vaccines effective at preventing severe infection, infectious disease doctor says
Posted at 1:08 PM, Nov 09, 2021
and last updated 2021-11-09 18:24:54-05

WELLINGTON, Fla. — Amanda Carr, 31, and Sean Cooley, 29, said they were both fully vaccinated against COVID-19 last spring.

"I had the Johnson & Johnson vaccine, the one and done," Carr said.

"I was able to get the Moderna vaccine," Cooley said.


Both of them got COVID-19 breakthrough cases.

"Two months later, in early June, I ended up with COVID," said Carr. "Unfortunately, it didn’t really go over so well for me. I ended up being a little more grateful for the fact I was vaccinated."

Amanda Carr, breakthrough COVID-19 case
Amanda Carr speaks about her bout with COVID-19 after getting vaccinated.

"I had a breakthrough case a few months ago and around 9 p.m. that night, I got really sick," Cooley said.

Dr. Larry Bush, an infectious disease specialist, explained what a COVID-19 breakthrough infection is.

"COVID breakthrough basically means that your immune system has been primed by the vaccine to fight this virus, and when you got exposed to the virus, it broke through your immune system," she said. "But that is not uncommon with other vaccines."

He said the vaccine is still doing its job.

"What is important is that the main goal of the vaccine was to keep you from getting very sick, hospitalized, dying," Bush said. "It still is very effective in the breakthroughs."

Dr. Larry Bush, infectious disease specialist
Dr. Larry Bush explains why some people contract COVID-19 despite getting the vaccine.

Cooley said he received monoclonal antibodies the day after testing positive.

"I immediately went into action mode, and how do I get better?" he said. "Within 12 hours, it was a 90 percent turnaround. I felt better really quickly."

Carr said she was one of the first breakthrough cases her doctors had seen, and she took a bit longer to recover.

"I had pretty awful symptoms," she said. "I was down and out for about seven days. There were a few times I thought I was going to have to go to the hospital."

Both said they still can't help but wonder — why and how?

"I am the only person I know who has gotten a breakthrough case," Cooley said.

Sean Cooley, breakthrough COVID-19 case
Sean Cooley explains what it was like getting a breakthrough infection of COVID-19.

"I do kind of question the 'one and done,' because I felt I didn't get enough of a reaction or any sort of protection," Carr said. "I had a lot of friends who had bad symptoms, and I had none."

Bush said it's not so clear-cut when it comes to side effects from the vaccine.

"I am the principal investigator of the J and J and AstraZeneca trial, and in those trials, we record every side effect and grade as mild, moderate, severe," he said. "But we also record everybody’s antibody levels, because that is being drawn every time you come. There is no correlation with side effects and antibody levels. So, even though you may have had a 103 fever and couldn't get out of bed for two days, your antibodies are no more robustly formed than someone who felt perfectly fine after the vaccine."

Both Cooley and Carr have a message.

"I can't imagine what it would've been like without the treatment or the vaccine," Cooley said.

"If it weren't for the vaccine, I don't think I would have maybe even survived COVID," said Carr. "It was pretty rough. I was scared of my breathing. I couldn't focus or concentrate, and I live alone, so for me, that's a risk."

Bush addressed questions people have about natural immunity versus vaccine protection.

"My answer is absolutely natural infection is important, but the studies show the vaccines seem to be better at preventing breakthroughs than people who had natural infection already," he said.

Bush explained who may be at a higher risk for breakthrough infections, pointing to why they especially need to get vaccinated.

"Those are elderly, immunocompromised, maybe pregnant women," he said. "If they do get infected, their natural immune system doesn't kick in as strongly, and therefore they may not do as well."

The bottom line is that Bush said the vaccines are effective at preventing severe infection.

"During this last surge we had in the hospital, it was nine to one unvaccinated to vaccinated that wound up in the hospital and certainly an even greater amount that got very sick were the unvaccinated," he said.

Bush also said, even if you are vaccinated, you need to take precautions.

"Don't let up on the other part of this process, which is common sense mitigation," Bush said. "That doesn't mean you have to wear a mask everywhere. That means when you are in a setting where there are a lot of people, your chance is greater."