The COVID-19 vaccines have been rightly celebrated for driving cases and hospitalizations down across the United States, but no vaccine on the planet offers absolutely perfect protection.
As of late April, the Centers for Disease Control and Prevention said there had been around 10,000 “breakthrough” cases among more than 100 million Americans who had been fully vaccinated at that time. (For those curious, that equates to less than 0.01% of people who got vaccinated.)
Because those infections have been so rare, however, there is a fair amount experts are still learning about the small number of cases that do happen. And one of the biggest questions right now is if you do experience a breakthrough case, is there a chance you could have long-haul COVID-19?
Here’s what we do — and don’t ― know so far.
Most breakthrough cases are mild.
Breakthrough COVID-19 cases among people who have been fully vaccinated (meaning they’re two weeks out from their second dose of the Pfizer or Moderna vaccine, or two weeks out from their Johnson & Johnson shot) tend to be pretty mild.
Based on the CDC’s preliminary data from April, about 30% of vaccine breakthrough infections were totally asymptomatic. An estimated 10% of people with breakthrough cases were hospitalized and 2% died, but it’s crucial to note that a decent portion of those hospitalizations and deaths were unrelated to COVID-19.
Experts do believe that while breakthrough infections are really rare, they also may be happening more often than the numbers suggest.
“Where the data gets a bit muddy is that there may be people who don’t get tested, because they think there’s no need because they have been vaccinated,” Cameron Wolfe, an associate professor of medicine at Duke University School of Medicine who specializes in infectious diseases, told HuffPost.
“There may be some folks who develop incredibly minor or asymptomatic cases of COVID that we just don’t pick up,” he added.
This, experts stress, is a sign that the vaccines are working. The main goal is to prevent severe disease and death. That’s why the CDC made the decision in May that it would no longer monitor all breakthrough COVID-19 infections, and instead focus strictly on cases in which the person is hospitalized or dies. Narrowing its focus allows the agency to put its energy into better understanding the most serious outcomes and what’s behind them, the CDC said.
But the change has not been without controversy. It means we are likely to understand less about the full range of what people experience when they get COVID-19 after being vaccinated, including people who may go on to develop longer symptoms.
As The New York Times recently pointed out: “Even relatively mild cases of COVID-19 can lead to persistent long-term health problems, and it will be difficult to know the full scope without tracking mild infections as well.”
The risk of ‘long-haul COVID’ seems low — but it’s too soon to say.
It’s not yet clear whether people who experience breakthrough infections are likely to grapple with long-haul COVID-19, or post-acute sequelae of SARS-CoV-2 (PASC). This can cause a range of symptoms that may last weeks or even months after a person is initially infected with the virus and can include everything from fatigue and dizziness to mental health problems.
But experts are optimistic that many of the people with a breakthrough case won’t endure long-haul COVID-19.
“There has not been, to my awareness, a swath of those people who are now coming forward with long-haul COVID symptoms despite being vaccinated,” Wolfe said. “In fact, quite the opposite. I think that whilst the numbers of hospitalizations and deaths compared to the number of vaccinated people is astronomically small, the cases that are picked up tend to be both minor and short-lived.”
That is true in terms of both symptom duration, Wolfe said, and how long those people tend to shed the virus. He pointed to the New York Yankees cluster from a few weeks ago, where several players and coaches tested positive for COVID-19 despite being fully vaccinated.
“They all did fine. They all had brief illnesses that were quite self-limited,” Wolfe said.
That said, he does have concerns about the potential for long-haul COVID-19 among people who are fully vaccinated and immunosuppressed. “A vaccinated patient getting chemotherapy can still get sick, and they can still get quite sick, because their response to the vaccine is so much less efficient,” Wolfe said.
There’s even some evidence that vaccination might help with long-haul COVID.
For months, informal polls conducted among social media support groups for people with “long COVID” have suggested that a fair number of patients — around 35% in some surveys — have experienced fewer symptoms after getting vaccinated.
More formal research is now beginning to back that up. A small, non-peer-reviewed study based in the United Kingdom recently found that more than half of people who were grappling with long-haul COVID-19 felt better post-vaccination.
Experts don’t really understand how that connection might work, but they’re calling for more research to look into it. “Since COVID-19 vaccinations appear to have the potential to improve the well-being of those with long-haul COVID, as well as provide protection from reinfection, we recommend that more structured, longitudinal trials take place,” the team behind the U.K. study wrote.
Whether or not breakthrough cases are linked to long-haul COVID, the need for more research is real.
Even if there is not ultimately a clear or strong connection between breakthrough coronavirus infections and longer symptoms, it’s just another aspect of long-haul COVID-19 that experts must continue exploring. People who experience long COVID not only have to deal with debilitating symptoms and chronic conditions that can last for months, they might even face a higher risk of death.
“It’s something that will need to continue to be followed,” Wolfe said. Though again, now that the CDC is only investigating severe breakthrough infections, it’s not clear who ― if anyone ― will do the tracking.
On the whole, doctors who are treating long-haul COVID-19 patients and those who have focused on chronic pain hope these issues will now get the attention they deserve.
Alexa Meara, a rheumatologist from Ohio State University Wexner Medical Center, told HuffPost that chronic and autoimmune issues — like long-haul COVID-19 now — have historically been underfunded and understudied, which she hopes will change.
“How do you measure fatigue? What is my fatigue to your fatigue? How do you objectively measure this? How do you measure pain? How do you measure functionality of life?” Meara said. “Fundamentally, these are difficult things to measure, which poses a conundrum for medicine.”
“COVID long-haul, in the sense of it being a post-viral syndrome, is not new,” she said. “However, in the way we’re approaching it, it’s 100% new because we have to create new systems, like COVID long-haul clinics that some institutions are creating, or helping people learn coping mechanisms.”
Experts are still learning about COVID-19. The information in this story is what was known or available as of publication, but guidance can change as scientists discover more about the virus. Please check the Centers for Disease Control and Prevention for the most updated recommendations.