Massive Longitudinal Study Of Ten Million Swedes Links COVID-19 To Heightened Risk Of Glandular Fever

A study of 10 million Swedes reveals that COVID-19 may weaken the immune system and trigger glandular fever, even in patients who had mild initial symptoms.

By: AXL Media

Published: Mar 17, 2026, 12:01 PM EDT

Source: Information for this report was sourced from Örebro University

Uncovering the Secondary Immunological Toll of the Pandemic

Evidence is mounting that the biological impact of a coronavirus infection extends far beyond the initial respiratory symptoms, potentially leaving the immune system in a persistently weakened state. A comprehensive study conducted by medical researchers at Örebro University suggests that individuals who tested positive for COVID-19 are at a higher risk of developing serious illnesses later, including glandular fever. According to Snieguole Vingeliene, a researcher in medicine and epidemiology at the university, the team was surprised to find that even those who did not experience severe symptoms during their initial viral encounter appeared to manifest signs of a compromised immune response in the following years.

The Tip of the Iceberg in Viral Reactivation

The research team tracked 10 million Swedish citizens ranging from age 3 to 100 between 2020 and 2022, creating one of the largest datasets on post-viral complications to date. The analysis specifically focused on patients whose glandular fever, caused by the Epstein-Barr virus (EBV), was severe enough to require hospitalization. However, Vingeliene notes that since many people with glandular fever do not seek hospital care, these findings likely represent only the most visible portion of a much larger public health issue. Because the Epstein-Barr virus remains in the human body for life after the initial infection, the researchers believe the coronavirus may act as a catalyst that reactivates the dormant virus or impairs the body's ability to keep it suppressed.

Vulnerability Across the Life Course and Younger Demographics

While Epstein-Barr is nearly universal, with nine out of ten Swedes carrying the virus, its progression into symptomatic glandular fever varies significantly by age and immune status. The study highlighted that a large portion of those who developed post-COVID complications were relatively young, suggesting that the coronavirus might have a particularly disruptive impact on the maturing immune systems of adolescents and young adults. This demographic shift is concerning for public health officials because glandular fever can result in profound exhaustion and fatigue that persists for months, often requiring extensive leaves of absence from education or employment.