Immunologists at the University Hospital Zurich found lower levels of two types of immunoglobulins among patients who developed post-acute Covid-19 syndrome, also known as Long Covid.

Normally levels of immunoglobulins IgM and IgG3 – antibodies produced by the immune system to fight infections – rise when a person catches Covid. But, along with risk factors such as age and a history of asthma, Zurich researchers detected lower levels of IgM and IgG3 in those Covid patients who still reported symptoms after four weeks. This has led the doctors to conclude that developing Long Covid correlates with a distinct Ig or antibody signature.

Their study, published this weekExternal link in the journal Nature Communications, followed 175 people who tested positive for Covid in the first wave of the pandemic. Forty other people who did not have the disease served as the control group.

The findings suggest that one cause of Long Covid, a little understood condition for which no standard definition or treatment exists, could be a misdirected immune response.

“This opens up possibilities for targeted treatments, such as the administration of certain immunoglobulins or immunomodulatory drugs,” lead researcher Odur Boyman told the Keystone-SDA news agency.

The best protection against Long Covid, however, is vaccination, said Boyman, because it reduces the risk of rapid viral replication and therefore a misdirected immune response.

The researchers have used their findings to develop a new model or score to calculate Long Covid risk that combines the antibody signature with age and a history of asthma in the patient. Determining immunoglobulin levels for the model can be done cheaply and easily, according to Boyman. The model was tested on another group of 395 Covid patients.

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