Sara Novak

With a number of large-scale clinical trials underway and researchers on the hunt for new therapies, long COVID scientists are hopeful that this is the year patients — and doctors who care for them — will finally see improvements in treating their symptoms.

Here are five bold predictions — all based on encouraging research — that could happen in 2024. At the very least, they are promising signs of progress against a debilitating and frustrating disease.

1: We’ll gain a better understanding of each long COVID phenotype

This past year, a wide breadth of research began showing that long COVID can be defined by a number of different disease phenotypes that present a range of symptoms.

Researchers identified four clinical phenotypes: Chronic fatigue-like syndrome, headache, and memory loss; respiratory syndrome, which includes cough and difficulty breathing; chronic pain; and neurosensorial syndrome, which causes an altered sense of taste and smell.

Identifying specific diagnostic criteria for each phenotype would lead to better health outcomes for patients instead of treating them as if it were a “one-size-fits-all disease,” said Nisha Viswanathan, MD, director of the long COVID program at UCLA Health, Los Angeles, California.

Ultimately, she hopes that this year her patients will receive treatments based on the type of long COVID they’re personally experiencing, and the symptoms they have, leading to improved health outcomes and more rapid relief.

“Many new medications are focused on different pathways of long COVID, and the challenge becomes which drug is the right drug for each treatment,” said Viswanathan.

2: Monoclonal antibodies may change the game

We’re starting to have a better understanding that what’s been called “viral persistence” as a main cause of long COVID may potentially be treated with monoclonal antibodies. These are antibodies produced by cloning unique white blood cells to target the circulating spike proteins in the blood that hang out in viral reservoirs and cause the immune system to react as if it’s still fighting acute COVID-19.

Smaller-scale studies have already shown promising results. A January 2024 study published in The American Journal of Emergency Medicine followed three patients who completely recovered from long COVID after taking monoclonal antibodies. “Remission occurred despite dissimilar past histories, sex, age, and illness duration,” wrote the study authors.

Larger clinical trials are underway at the University of California, San Francisco, California, to test targeted monoclonal antibodies. If the results of the larger study show that monoclonal antibodies are beneficial, then it could be a game changer for a large swath of patients around the world, said David F. Putrino, PhD, who runs the long COVID clinic at Mount Sinai Health System in New York City.

“The idea is that the downstream damage caused by viral persistence will resolve itself once you wipe out the virus,” said Putrino.

3: Paxlovid could prove effective for long COVID

The US Food and Drug Administration granted approval for Paxlovid last May for the treatment of mild to moderate COVID-19 in adults at a high risk for severe disease. The medication is made up of two drugs packaged together. The first, nirmatrelvir, works by blocking a key enzyme required for virus replication. The second, ritonavir, is an antiviral that’s been used in patients with HIV and helps boost levels of antivirals in the body.

In a large-scale trial headed up by Putrino and his team, the oral antiviral is being studied for use in the post-viral stage in patients who test negative for acute COVID-19 but have persisting symptoms of long COVID.

Similar to monoclonal antibodies, the idea is to quell viral persistence. If patients have long COVID because they can’t clear SAR-CoV-2 from their bodies, Paxlovid could help. But unlike monoclonal antibodies that quash the virus, Paxlovid stops the virus from replicating. It’s a different mechanism with the same end goal.

It’s been a controversial treatment because it’s life-changing for some patients and ineffective for others. In addition, it can cause a range of side effects such as diarrhea, nausea, vomiting, and an impaired sense of taste. The goal of the trial is to see which patients with long COVID are most likely to benefit from the treatment.

4: Anti-inflammatories like metformin could prove useful

Many of the inflammatory markers persistent in patients with long COVID were similarly present in patients with autoimmune diseases like rheumatoid arthritis, according to a July 2023 study published in JAMA.

The hope is that anti-inflammatory medications may be used to reduce inflammation causing long COVID symptoms. But drugs used to treat rheumatoid arthritis like abatacept and infliximabcan also have serious side effects, including increased risk for infection, flu-like symptoms, and burning of the skin.

“Powerful anti-inflammatories can change a number of pathways in the immune system,” said Grace McComsey, MD, who leads the long COVID RECOVER study at University Hospitals Health System in Cleveland, Ohio. Anti-inflammatories hold promise but, McComsey said, “some are more toxic with many side effects, so even if they work, there’s still a question about who should take them.”

Still, other anti-inflammatories that could work don’t have as many side effects. For example, a study published in The Lancet Infectious Diseases found that the diabetes drug metformin reduced a patient’s risk for long COVID up to 40% when the drug was taken during the acute stage.

Metformin, compared to other anti-inflammatories (also known as immune modulators), is an inexpensive and widely available drug with relatively few side effects compared with other medications.

5: Serotonin levels — and selective serotonin reuptake inhibitors (SSRIs) — may be keys to unlocking long COVID

One of the most groundbreaking studies of the year came last November. A study published in the journal Cell found lower circulating serotonin levels in patents with long COVID than in those who did not have the condition. The study also found that the SSRI fluoxetine improved cognitive function in rat models infected with the virus.

Researchers found that the reduction in serotonin levels was partially caused by the body’s inability to absorb tryptophan, an amino acid that’s a precursor to serotonin. Overactivated blood platelets may also have played a role.

Michael Peluso, MD, an assistant research professor of infectious medicine at the UCSF School of Medicine, San Francisco, California, hopes to take the finding a step further, investigating whether increased serotonin levels in patients with long COVID will lead to improvements in symptoms.

“What we need now is a good clinical trial to see whether altering levels of serotonin in people with long COVID will lead to symptom relief,” Peluso said last month in an interview with Medscape Medical News.

If patients show an improvement in symptoms, then the next step is looking into whether SSRIs boost serotonin levels in patients and, as a result, reduce their symptoms.