New studies on long COVID-19 provide no definitive answers

Dear Doctors: I get why people are totally over dealing with COVID-19, but I don’t have that luxury. I’m 31 years old, and I thought I was lucky when my case of COVID-19 only felt like a bad cold. But it’s been six months now, and I’m still sick. Have we learned anything new about what causes long COVID-19?

Dear Reader: As most of us probably know by now, “long COVID-19” refers to the long-lasting health problems that affect a sizable number of those who have been ill with COVID-19.

The official name for the syndrome is “post-acute sequelae of SARS-CoV-2 infection,” or PASC. It consists of a shifting constellation of a wide range of symptoms. These include fever, headache, chronic cough, shortness of breath, a racing or disordered heartbeat, stomach pain, gastroenteritis, changes to menstrual cycle, dizziness, brain fog, insomnia, changes to mood and persistent fatigue or exhaustion. Symptoms last for weeks, and often for many months, after the initial illness has passed.

When long COVID-19 first emerged, it appeared to occur mainly in those who experienced severe illness. We now know that anyone who becomes infected with SARS-CoV-2, which is the name of the coronavirus that causes COVID-19, can go on to develop the syndrome.

Data from several new studies into long COVID-19 have just been released. While there has not yet been a definitive breakthrough regarding the cause, the results of the research continue to chip away at this baffling illness.

One study, conducted by the Centers for Disease Control and Prevention, found that long COVID-19 occurs in about 20% of adult COVID-19 survivors under the age of 65, and up to one-fourth of those over the age of 65. In the older group, risk of developing long COVID-19 increased with age.

For some long COVID-19 patients, like yourself, symptoms of the initial disease never fully resolve. In others, who have recovered from their illness, symptoms return, sometimes as long as six months later. Another study found that having been vaccinated produced a mild protective effect against long COVID-19 but did not eliminate the risk of developing the disease.

Elizabeth Ko, MD and Eve Glazier, MD

Research conducted by the National Institutes of Health looked into whether the syndrome might be caused by lingering fragments of virus, whose presence could trigger the immune system to fight the disease all over again. Unfortunately for those hoping for a definitive answer to the mystery of what causes long COVID, the study did not find evidence of that.

Now researchers are looking to the intense immune response that occurs in some individuals as a potential factor in the cause of lingering disease. It is possible that, after revving up to such a high level, the immune system never fully settles back down. Meanwhile, a seasonal pattern of COVID-19 infections has emerged. As with the flu, the disease is always present. But epidemiologists, including colleagues here at UCLA, have begun referring to COVID-19 as a seasonal illness, with surges occurring in summer and winter.

We know we’re repeating ourselves here, but we urge our readers to please remain vigilant in protecting themselves and their loved ones from infection.

To learn more about the vaccines and for the latest information visit UCLA Health's COVID-19 Vaccine Info Hub.

(Send your questions to askthedoctors@mednet.ucla.edu. Owing to the volume of mail, personal replies cannot be provided.)


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