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For nearly three years, scientists have worked tirelessly to unravel the mysteries of the long-running COVID—while ever-increasing numbers of people struggle with its lingering, life-altering symptoms.
It is officially known as state after COVID-19a constellation of 200 or more medical problems that can persist or occur months after the initial infection, ranging from fatigue to shortness of breath to a feeling of “brain fog.”
For some, a long COVID can equate to several months of frustration. For others, it leads to debilitating health effects that never seem to resolve. This range of possibilities has many sufferers wondering: How long does COVID really last?
A new, large-scale study from Israel is the latest to examine the spectrum of symptoms, who is affected and for how long.
Published in the British Medical Journal on Wednesdaythe peer-reviewed study looked at nearly two million medical records and matched about 300,000 people who had laboratory-confirmed infections with another 300,000 who did not test positive for SARS-CoV-2.
The researchers found that different types of health problems after a mild case of COVID persist for several months but disappear within the first year after infection.
Some symptoms, including weakness and difficulty breathing, are more likely to persist.
“There are patients who experience long-term symptoms of COVID for a year and their lives are changed and they suffer — we know that,” said Dr. Maital Biwas-Benita, a senior researcher at the KI Research Institute in Kfar Malal, Israel.
“But when we look at this large population and look at their medical records, what we see is a small number of symptoms that persist, and we see that they decrease over time.”
WATCH | Most lingering symptoms of COVID disappear within a year, new research shows:
Most lingering symptoms of COVID disappear within a year, new research shows
New research from Israel suggests that most symptoms of prolonged COVID disappear within a year, but some — such as weakness and breathing problems — are more likely to persist.
Breathing problems, weakness is more likely to continue
The study looked at dozens of different health effects associated with prolonged COVID, including rashes, dizziness, hair loss, palpitations, chest pain, abdominal pain.
The team also divided their findings into two time frames: the first three to six months after infection and the following six months.
The most common health problem after COVID? Difficulty breathing, according to the study.
But that was far from the only common complaint. Others, including hair loss, persisted only in the first months after infection, the findings suggest, while breathing problems, weakness, dizziness and a feeling of brain fog were among those that persisted for up to a year.
“They looked too [being] vaccinated versus not,” said University Health Network clinician-scientist Dr. Angela Cheung, who treats long-term COVID patients at a Toronto clinic. “And those who got vaccinated also had fewer symptoms, specifically the problem out of breath.”
This is not the first study to suggest that vaccination can reduce the long-term risks of COVID. Earlier American studies, published in the journal Nature Medicine last Mayfound that vaccination can reduce the chance of prolonged COVID by approximately 15 percent.
Findings do not include Omicron
Indeed, the study – like all scientific research – has its strengths and weaknesses.
The large amount of medical records gave the team the ability to compare people with SARS-CoV-2 infections to an uninfected control group, so they could match subjects based on factors such as their age and pre-existing health conditions. This allowed the team to understand which symptoms were likely caused by the infection itself.
“You want to see the difference that COVID added,” said Barak Mizrahi, another senior researcher at the KI Research Institute who worked on the study.
On the other hand, his colleague Bivas-Benita stressed that the use of medical records may also mean that the results are underestimated for people with unresolved health problems, because those who did not seek medical help were not included. (The researchers also excluded hospitalized patients to focus on mild infections.)
In the paper, the researchers also note that there may have been underreporting of symptoms in the later periods of the study.
And most importantly, the study period only extended from March 2020 to October 2021, so the findings do not include the currently circulating Omicron variant, which caused a huge wave of cases in Canada in early 2022.
“This study looked mainly at the Delta variant time frame, not the Omicron,” Cheung said.
“People get better with time”
While the data may be from an earlier phase of the pandemic, several Canadian long-term COVID researchers — who were not involved in the study — say it adds another piece to the puzzle.
“Yes, it’s retrospective, yes, it’s from medical records, but what it shows us is that people really do improve over time, which is an important thing for people to remember,” said Cheung, who also added, that some of her patients have been dealing with post-COVID health effects for more than two years.
Most important, says McMaster University immunologist Manali Mukherjee, is the Israeli team’s use of a control population of those who were not infected within a large sample size.
“This is exactly the kind of training you need,” she said.
The findings follow Mukherjee’s own research, published in the journal European Respiratory Medicine last fall.
Using a much smaller sample of roughly 100 patients in Canada, Mukherjee’s team showed that roughly three-quarters of those infected with SARS-CoV-2 recovered within a year, regardless of the severity of their illness, while others faced ongoing symptoms of cough, fatigue and difficulty breathing.
WATCH | WHO calls for ongoing long-term study of COVID:
Long COVID needs much more research, says WHO
More research is needed to understand the scale and severity of prolonged COVID and how to help rehabilitate patients, says Maria Van Kerkhove of the World Health Organization.
But that study was also limited by its small sample size and, like the Israeli paper, only looked at the time period before Omicron’s arrival.
Mukherjee’s research also found that patients with persistent symptoms had antibodies associated with autoimmune diseases and elevated levels of cytokines — small proteins that are a key part of the body’s cellular communication network — which can trigger inflammation.
Speaking to CBC News, Mukherjee — herself a long-term COVID sufferer — said this is just one of many possible mechanisms being explored to explain the range of long-term symptoms of COVID. while others look at possible ripple effects from problems like small blood clots.
“The reason you have so many different theories is because you have so many different representations of it,” she said.
The rate of prolonged COVID is probably decreasing
Many presentations, different time frames and severity range – all these factors make studying a long COVID a challenging proposition.
The new Israeli study notably avoids any breakdown of exactly what percentage of people recover within a year and what percentage don’t. That, the researchers said, isn’t the goal, nor something that’s easy to do given the wide spectrum of post-COVID illnesses.
Until now, there is a large estimate of how many people are affected. The World Health Organization (WHO) maintains about 10 to 20 percent of people infected with SARS-CoV-2 may develop symptoms that can be diagnosed as prolonged COVID. Other estimates over the years range from a small percentage of cases to over 30 or 40 percent.
As CBC News previously reportedmore research suggests, reassuringly, that rates of sustained COVID are now lower than previously thought, possibly thanks to rising levels of immunity through vaccinations.
WATCH | Doctors try to understand the long COVID:
Doctors are looking to solve the long COVID while patients struggle to recover
Nearly two years after the start of the COVID-19 pandemic, doctors and health experts are searching for a cause and a cure for the lingering COVID, while patients simply struggle to recover.
Early findings using self-reported, app-based data from a team in the UK found a reducing the chances of prolonged COVID with the Omicron variant compared to the Delta.
Similarly, a Canadian study of COVID showed that while 26 percent of adults reported symptoms at least three months after infection before December 2021. which dropped to 11 percent after December 2021 — although in both cases the self-reported data comes with limitations, and neither contains reports from patients for a year or more to show long-term effects.
Because so much remains to be understood about this condition, WHO is calling for continued global funding and research.
“There’s still a lot of work to be done in this space, including recognition, research and rehabilitation,” WHO’s technical lead for COVID-19, Dr. Maria Van Kerkhove, said in response to a question from CBC News on Wednesday.
Katie McLean, a 44-year-old Vancouver resident who has battled a long list of COVID symptoms since contracting the virus in September 2020, hopes all the studies showing most people recover won’t dissuade researchers from investigate this condition further.
More than two years after he first became ill, McLean still struggles with fatigue and weakness, relies on a cane and is unable to return to work.
“My biggest concern would be that the pandemic continues and more and more people find themselves in my shoes – and there is no answer,” she said.
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