Can Vaccinated People Become COVID Long Haulers?

Long-term COVID-19 symptoms might be possible among fully vaccinated people who develop a breakthrough infection, preliminary reports show. Sometimes called long-haul COVID, long COVID is when symptoms last beyond 28 days.

Although instances have been reported, researchers say more studies are needed to determine whether long COVID is occurring after breakthrough cases and to what extent.

“If it is found that breakthrough infections can lead to long COVID, the public needs to know that,” Daisy Massey, post-graduate associate at the Center for Outcomes Research and Evaluation (CORE) at Yale University School of Medicine, tells Verywell. “And I think it’s such nuanced messaging. It’s really hard to convey how powerful the vaccine is and yet the importance of not letting your guard down.”

Preliminary Reports of Vaccinated Long Haulers 

More than 9 in 10 COVID-19 cases, hospitalizations, and deaths in the U.S. have occurred in people who are unvaccinated or not yet fully vaccinated, according to a recent analysis of available state data from the Kaiser Family Foundation (KFF).

That analysis backs up previous reports about vaccine efficacy. The available COVID-19 vaccines are highly effective at preventing severe disease and death, but they aren’t 100% effective. Breakthrough infections, which are generally mild or asymptomatic, do occur.

The concept of breakthrough infections raised an important question for Diana Berrent, founder of Survivor Corps, a grassroots community of nearly 170,000 members focused on COVID-19 patient support and research: Could people with breakthrough infections develop long COVID? So Berrent sent out a poll to the group.

Berrent and researchers from the Yale School of Medicine, including Massey, compiled a report based on the public poll. The poll garnered responses from 1,949 people reporting they were fully vaccinated. Of those participants, 44 said they had contracted a symptomatic breakthrough infection. And of those reported breakthrough cases, 24 said they had developed symptoms of long COVID. One individual who reported symptoms of long COVID also reported being hospitalized. The report, available as a preprint, has not yet been peer reviewed.

“It’s really a first glance and a call for more attention,” Massey says, “rather than knowledge that we can share to tell people what levels of risk they would face.”

Massey says the results are gleaned from a biased sample and cannot be used to conclude that long COVID is occurring with breakthrough cases. But shortly after the preprint release, a study published in the New England Journal of Medicine also raised concerns.

“It’s a small study of healthcare workers in Israel who had been vaccinated and some of whom were found to have breakthrough infections with long COVID,” Massey says. 

The study found 39 breakthrough infections among 1,497 fully vaccinated healthcare workers. All infected individuals had mild symptoms and did not require hospitalization. But 19% had symptoms lasting longer than six weeks post-diagnosis.

“The potential for breakthrough cases of infection in vaccinated people leading to long-haul symptoms is critically important,” Brooks B. Gump, PhD, MPH, Falk Family Endowed Professor of Public Health at Syracuse University, tells Verywell. “It shows how much we still have to learn and the reason for caution when facing unknowns.” 

Massey says the Centers for Disease Control and Prevention (CDC) is conducting post-vaccination cohort studies regarding breakthrough infections and long COVID.

The Importance of Long COVID Research

Long COVID is unpredictable. Severity of initial COVID-19 symptoms doesn’t determine whether someone will have lingering illness or the intensity of any post-COVID symptoms. 

“We know with long COVID that a lot of young people get it,” Massey explains. “A lot of people who have mild cases get it. People who are completely asymptomatic—like one of the patients in our study—can then be in a wheelchair because of long COVID.”

A study published in The Lancet shows how long COVID can impact quality of life. Researchers analyzed data collected from 3,762 survey participants with confirmed or suspected COVID-19 and with illness lasting more than 28 days. The study estimated 203 long COVID symptoms across 10 organ systems.

“There’s such a breadth of long COVID experiences,” Massey says. “Some of them are completely debilitating.”

For more than 90% of participants, symptoms lasted longer than 35 weeks. The most frequent symptoms after six months included fatigue, cognitive dysfunction, and post-exercise malaise. More than 45% of responders needed a reduced work schedule, and more than 22% were not working at all as a result of ongoing illness.

The data was collected prior to vaccine availability, so none of the participants had a breakthrough case. But the research shows the importance of preventing COVID-19 infection. And experts say the currently available vaccines are still our best tools for doing that. 

“We do know that you’re way more likely still to be infected if you don’t get the vaccine than if you do,” Massey says. “And we’ll find out more specifically about breakthrough infections and how they differ from non-breakthrough infections as we get more data.”

How Common Are Breakthrough Cases? 

As of July 26, more than 163 million people in the United States were fully vaccinated against COVID-19. The CDC reports that 6,587 people with breakthrough infections died or were hospitalized.

However, 1,598 of the patients hospitalized had asymptomatic infection and were admitted for unrelated reasons. And 309 of the people who died also had asymptomatic infection and died from unrelated causes. Therefore, about 4,680 out of 163 million fully vaccinated people had a more severe breakthrough case involving hospitalization or death.

The currently available vaccines are effective, but not 100% at preventing illness, so breakthrough infections are expected,” Hannah Sally, MSc, senior epidemiologist at Informa Pharma Intelligence, tells Verywell. “The vaccines certainly prove effective at reducing severe COVID-19 infections.”

The CDC continues to track breakthrough cases in vaccinated patients who were hospitalized or who died. But the agency stopped collecting data from states on other breakthrough infections as of May 1.

“Due to lack of reporting, there is limited data on the number of mild infections in fully vaccinated people,” Sally says. The CDC also acknowledges that breakthrough cases in general are likely underreported.

A KFF analysis looked at available state data. The analysis shows that breakthrough cases, hospitalizations, and deaths are rare among the fully vaccinated in all reporting states. Rates are all well below 1%.

Increased Community Transmission Increase the Odds of Breakthrough Cases

The 7-day moving average of daily COVID-19 new cases has steadily risen since late June. And community transmission is high in many places, according to the CDC COVID Data Tracker.

“If you have such high community spread,” Massey says, “even if the vaccines are really strong, that community spread is going to continue among the unvaccinated and eventually to some of the vaccinated as well.” 

With the more infectious Delta variant circling, the CDC has updated its guidance for fully vaccinated people. The latest recommendation is to wear a mask in public indoors settings in areas of substantial or high transmission.

“Saying that we should take risk mitigation steps like wearing masks in addition to [getting] the vaccine is not a knock on the vaccine,” Massey says, “but a knock on vaccination rates and on how much COVID is spreading.” 

Currently, about half of the total U.S. population is fully vaccinated for COVID-19, according to the CDC COVID Data Tracker. And just under 60% of the population 12 and older is fully vaccinated. Getting vaccination rates up will help mitigate instances of breakthrough infections, Massey says.

“Combining solutions is only smart,” she adds. “Throwing everything we have at protecting ourselves and kids and immunosuppressed people and the elderly is only smart.”