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6 Things You Must Know About Breakthrough Covid-19 Infections

by Rachel Nania, AARP, Updated July 27, 2021


Catching the coronavirus after being fully vaccinated is unlikely, but it happens. Here's why.


"Breakthrough” is the new pandemic buzzword. Reports of Americans testing positive for COVID-19 despite being fully vaccinated have been making headlines lately — from the halls of Congress to Yankee Stadium to summer celebrations at the tip of Cape Cod. But are these cases, which seem to be popping up more frequently, cause for concern?


Here's what the experts have to say about breakthrough infections.


1. Breakthrough cases are normal


No vaccine is 100 percent effective at preventing disease. But the shots authorized in the U.S. to help quell COVID-19 are pretty close — especially when it comes to thwarting severe illness and death, which is what they were designed to do.

In fact, less than 1 percent of fully vaccinated individuals have been hospitalized with, or have died from, COVID-19, according to the latest data tracked by the Centers for Disease Control and Prevention (CDC). When it comes to older adults, who were hit hardest by the coronavirus during its initial sweep, fully vaccinated individuals ages 65 and up are 94 percent less likely to be hospitalized with COVID-19 than people of the same age who are not vaccinated.


And while it's unclear how many vaccinated individuals come down with an asymptomatic or mild case of COVID-19 — the more likely scenario if you do get a breakthrough infection — it's safe to assume the risk is also on the smaller side, explains Christopher Ohl, M.D., professor of infectious diseases at the Wake Forest School of Medicine. “It's not common, but it happens,” he says.

The important thing to keep in mind is that when these cases occur, “by no means does that mean that you're dealing with an unsuccessful vaccine,” Anthony Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases, said in a recent press briefing. “The success of the vaccine is based on the prevention of [more serious] illness.”


2. Delta variant is partially to blame


Breakthrough infections may become more prevalent, however, as the highly contagious delta variant blazes through unvaccinated communities. (About half of the country is still unvaccinated.)


That's not because the vaccines don't work against the now-dominant strain, which is responsible for more than 80 percent of new COVID-19 cases in the U.S. Studies show that while the immune response is somewhat diminished against delta compared to other virus variants, the vaccines are still holding their ground when a full dose regimen is completed. Rather, it has to do with frequency of exposure.


"Think of the vaccine as reducing your risk of getting infected in any given encounter by something like 90 percent,” says David Dowdy, M.D., associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health. If you're in a situation where there are more cases of COVID-19 and you're having closer interactions with people, “then we expect more breakthrough infections — not because the vaccines aren't working but just because people are being exposed [to the virus] more often,” he adds.


Leana Wen, M.D., an emergency physician and visiting professor of health policy and management at George Washington University's Milken Institute School of Public Health, has likened the vaccines to a very good raincoat. “If it's drizzling outside, you're going to be fine; you will be protected and not get wet. However, if you keep going in and out of thunderstorms, at some point you could get wet,” she told AARP in a recent interview.


3. ‘Return to normal’ adds to breakthrough risk


As Americans both vaccinated and unvaccinated return to the workplace and resume pre-pandemic activities, there are more opportunities to be exposed to the coronavirus. In many regions of the country, the numbers bear out the consequences.


As of July 22, 35 percent of U.S. counties were experiencing high levels of community transmission, and new cases of COVID-19 were on the rise in 90 percent of U.S. jurisdictions. Overall, cases in the U.S. climbed 46.7 percent between July 12 and July 19; an average of more than 64,000 infections are now being reported daily, CDC data show. (A month ago, this number was closer to 10,000; at the peak of the pandemic, daily case counts registered above 200,000.)

Complicating matters is the easing of prevention measures. Practices that had been in place — masks, physical distancing, restrictions on indoor gatherings and so on — have been curtailed or abandoned by many.


“Three, four months ago, people were still being very cautious about this virus. Whereas now, many people are acting a lot less cautiously,” Dowdy says.


Even without delta in the mix, Ohl says, we'd likely still be seeing a rise in breakthrough cases this summer amid the return to pre-pandemic behavior and stalled vaccination efforts. “It wouldn't be quite as many, but it would still be happening,” he says, “just because we're not taking any precautions."


The CDC, however, updated its mask guidance on July 27 to recommend that fully vaccinated individuals who live in or visit areas where coronavirus cases are surging wear a mask when in indoor public settings. Teachers, students, staff and visitors at schools are also advised to mask up, regardless of vaccination status, as new data shows that “in rare occasions, some vaccinated people infected with the delta variant after vaccination may be contagious and spread the virus to others,” CDC Director Rochelle Walensky said in a press briefing.


4. Link between breakthrough cases and long COVID is unclear


Millions of people who have had COVID-19 have also reported lingering symptoms, ranging from shortness of breath to difficulty thinking to joint and muscle pain. It's become such a common effect of the disease that clinics have popped up all over the country to study the phenomenon and help these patients get back to normal.


But it's still unclear whether a breakthrough coronavirus infection can result in what's commonly referred to as “long COVID.” Fauci said in a July 22 briefing that it's “an object of a very intensive study right now.”


However, some experts are betting that the odds of developing long COVID after you're fully vaccinated are slim. “There's good reason to believe that the more serious your infection is, the greater risk you are of having longer-term sequelae” — a word that refers to a condition resulting from an illness, Dowdy says.


"And since the vaccines are particularly good at preventing infections from getting out of hand when they do occur, there's strong reason to believe that these vaccines will also be very effective in preventing these sorts of long-term sequelae,” he adds.


5. Testing is critical as cold and flu season looms


If you are fully vaccinated and start to feel ill, getting a test to determine the cause is increasingly important — especially with colds on the rise and flu season right around the corner, Ohl says. If it's the flu, there's antiviral medicine that can help relieve symptoms. (Currently, there is no easy-to-prescribe pill to treat COVID-19, but there could be soon.)


If it's COVID-19, “you're going to need to isolate and take precautions to not give it to other people, particularly vulnerable people,” Ohl says. Researchers are still trying to understand whether vaccinated people who test positive for COVID-19 can pass the virus on to others. Some studies show the likelihood is pretty low, but precautions should still be followed, particularly if you live with someone who is unvaccinated.


"And if it's a cold, then you can just do what you normally would do with a cold. So you kind of need to know what's causing these mild symptoms,” Ohl adds.


6. More vaccinations mean fewer breakthrough cases


The best way to protect yourself from getting COVID-19 is to get vaccinated. And as more people roll up their sleeves to get the shots, we'll likely start to see fewer breakthrough infections.

"Largely, the breakthrough infections come from a vaccinated person being exposed to an unvaccinated person who has COVID,” Ohl says. “Think of it like we're going to have the virus do a mud run. ... The more people that get vaccinated, the thicker and deeper the mud is, and the likelihood of the virus being transmitted between people gets less and less and less.”

In the meantime, as new cases shoot up across the country, “there is a reason for us all to be a bit more cautious about things,” Dowdy says. More virus circulating in the community “puts all of us at more risk.”

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