We now know a major cause of multiple sclerosis. Can we eradicate it?

Several chronic or life-threatening diseases have their origin in a common viral or bacterial infection. Approximately two-thirds of the world population is infected with the bacterium Helicobacter pylori, which significantly increases the risk of developing gastric cancer. Similarly, high-risk types of human papillomavirus cause nearly all of cervical cancers. A recent large-scale study has now shown for the first time that Epstein-Barr virus (EBV) might be the main cause of multiple sclerosis. It is one of the most common human viruses: About 90% of people worldwide will be infected during their lifetime, generally causing few, if any, symptoms.

Multiple sclerosis (MS) is a chronic disease affecting the central nervous system (the brain and spinal cord). It occurs when the immune system attacks nerve fibres and myelin sheathing (a fatty substance which surrounds/insulates healthy nerve fibres) in the brain and spinal cord. This attack causes inflammation, which destroys nerve cell processes and myelin – altering electrical messages in the brain. MS is unpredictable and affects each patient differently – some individuals may be mildly affected, while others may lose their ability to write, speak or walk.

The risk of MS increased 32-fold after infection with EBV, but was unchanged after infection with other viruses, providing the first compelling evidence for EBV as the leading cause of the disease; something that has been suspected for many years.

These insights open a door to new prevention and treatment options for this uncurable disease or even an opportunity for eradication. Current MS-modifying treatments are costly and can exceed $70,000 per year in the US, with this significant spending limiting access and putting an additional burden on patients. Low- and middle-income countries suffer from significant access gaps, with poor availability of medications resulting for example in less than 35% of MS patients in Latin America having access to disease-modifying treatments.

A vaccine against the initial Epstein-Barr virus could not only prevent the disease from developing, but also significantly reduce global healthcare costs, and improve equitable access and the sustainability of health systems. While there are currently no EBV vaccines on the market, the first clinical trials have recently been initiated. The exploratory vaccine is based on the new mRNA technology, which has delivered two successful COVID-19 vaccines.

The World Health Organization (WHO) considers vaccines to be one of the most successful and cost-effective public health interventions; equitable access to these vaccines will be crucial to deliver the full benefit across the globe. According to Dr Tedros Ghebreyesus, Director-General of the WHO, “vaccine equity is the challenge of our time”, yet “vaccine inequity is a solvable problem”.