Long COVID study outlines possible causes and potential treatments

The impact of the COVID pandemic on NHS workers and patients is being looked at by a public inquiry.

The first public hearings of the third stage – "module three" – of the UK COVID-19 Inquiry were held on Monday and will examine the impact of the pandemic on how NHS services were delivered.

As part of this, it will also scrutinise how long COVID was diagnosed and how much support has been offered to those affected.

A series of studies this year have pointed to possible explanations behind 'long COVID' - along with potential measures to treat it.

How many people have long COVID?

According to data released by the Office for National Statistics (ONS) in April, two million people in England and Scotland were still suffering the effects of "long COVID" - the term used to describe the effects of the virus that continue for weeks or months beyond the initial illness.

Almost a third of those (30.6%) had been suffering symptoms for three years, the ONS said.

A University College London (UCL) study this year found that pain is the most common symptom of long COVID, with 25.6% of participants, followed by anxiety and depression, (18.4%), fatigue (14.3%) and shortness of breath (7.4%).

In April, a University of York study that reviewed 17 studies from around the world, found that the risk of long COVID varies enormously, from 3% to 75%. The study suggests that on average, 9% of people who catch COVID-19 may be at risk of developing Long COVID.

Are people still contracting long COVID?

Earlier this month, a study led by Ziyad Al-Aly, chief of research and development at the Veterans Affairs St Louis Health Care System, found that the number of people contracting long COVID had dropped but still remains high.

At the onset of the pandemic, roughly 10% of people who contracted the coronavirus went on to develop long COVID. Today, that figure is around 3.5% among vaccinated people.

But with around 1.3 million people in the US being infected daily, there are still a significant number of people affected by long COVID.

Al-Aly said: “You do the math – 3-4% of those people is a huge number of potential long COVID patients being added to the roster.”

What treatments work?

The study, led by Al-Aly’s team, found that the decline in long COVID is largely due to vaccinations – with 70% of the decline attributable to vaccines.

Vaccines reduce the risk of severe infection and long-lasting infection, thereby cutting the risk of sufferers developing long COVID, researchers believe. Maintaining vaccine uptake is critical to cutting the numbers of long COVID sufferers, they add.

Has science found the cause of long COVID?

One recent study found that one of the main causes of respiratory symptoms could be linked to clotting and inflammation in the blood vessels of the lungs.

A study published in Nature this August found that two chemicals in blood that play a role in clotting (fibrinogen and fibrin) and abnormal clotting could be linked to long COVID symptoms.

The researchers found that fibrin and fibrinogen bind to the spike protein of the virus that causes COVID, driving inflammation and problems in the lungs and brain.

It’s possible that an antibody could prevent this process.

Another study with mice found that rodents infected with influenza have similar clusters of cells in their lungs - and that blocking an overactive immune response can reduce scarring and restore lung function.

Harish Narasimhan, a PhD candidate in Immunology at the University of Virginia, said: "Using our new mouse model, we were able to identify the presence of an abnormal cluster of cells in mice lungs – made up of the same dysfunctional immune and epithelial, or structural, cells seen in the lungs of long COVID-19 patients.

"Additionally, we found that the uncontrolled activity of these immune cells in the lungs impeded structural cells from repairing themselves. It also hindered them from restoring gas exchange, the process of taking in oxygen and releasing carbon dioxide.

"Importantly, when we blocked the activity of proteins associated with this overactive immune response, it reduced lung scarring and restored optimal lung function in mice."