During its June 2025 meeting, the Pharmacovigilance Risk Assessment Committee (PRAC) of the European Medicines Agency (EMA) concluded its review of medicines containing semaglutide following concerns regarding a possible increased risk of developing non-arteritic anterior ischemic optic neuropathy (NAION).
Furthermore, the PRAC is reviewing the known risk of encephalitis (inflammation of the brain) with two varicella (chickenpox) vaccines, Varilrix and Varivax, following a report of a fatal outcome after vaccination with Varilrix.
Medicines containing semaglutide
The PRAC concluded its review of medicines containing semaglutide following concerns regarding a possible increased risk of developing non-arteritic anterior ischemic optic neuropathy (NAION), an eye condition that may cause loss of vision. Semaglutide, a GLP-1 receptor agonist, is the active substance in certain medicines used in the treatment of diabetes and obesity (namely Ozempic, Rybelsus and Wegovy).
After reviewing all available data on NAION with semaglutide, including data from non-clinical studies, clinical trials, post-marketing surveillance and medical literature, the PRAC has concluded that NAION is a very rare side effect of semaglutide (meaning it may affect up to 1 in 10,000 people taking semaglutide).
Results from several large epidemiological studies suggest that exposure to semaglutide in adults with type 2 diabetes is associated with an approximately two-fold increase in the risk of developing NAION compared with people not taking the medicine. This corresponds to approximately one additional case of NAION per 10,000 person-years of treatment; one person-year corresponds to one person taking semaglutide for one year. Data from clinical trials also point to a slightly higher risk of developing the condition in people taking semaglutide, compared with people taking a placebo (a treatment with no active ingredients).
The EMA has therefore recommended that the product information for semaglutide medicines be updated to include NAION as a side effect with a frequency of ‘very rare’. If patients experience a sudden loss of vision or rapidly worsening eyesight during treatment with semaglutide, they should contact their doctor without delay. If NAION is confirmed, treatment with semaglutide should be stopped.
In Belgium, the medicines containing semaglutide are authorised and commercially available under the following brand names :
o Ozempic
o Rybelsus
o Wegovy
More information regarding this communication is available on the EMA website.
Varicella vaccines
The PRAC is reviewing the known risk of encephalitis (inflammation of the brain) with two varicella (chickenpox) vaccines, Varilrix and Varivax, following a report of a fatal outcome after vaccination with Varilrix.
Varilrix and Varivax are authorised for vaccination of adults and children from 12 months of age, and in certain populations from 9 months of age, against chickenpox. They contain live attenuated (weakened) varicella virus. In Belgium, the varicella vaccines Varilrix and Varivax are both available.
Varicella is caused by the varicella-zoster virus, which also causes shingles (herpes zoster). Varicella mainly affects children aged 2 - 8 years and is usually a mild disease from which children recover quickly. In some cases, varicella can cause complications including bacterial infection of the skin or blood, pneumonia (infection and inflammation of the lungs) and encephalitis. Encephalitis can also be caused by other viral or bacterial infections. While most people with encephalitis recover, the condition can be life-threatening.
This review was initiated by the PRAC following a case report in Poland of a child who developed encephalitis a few days after receiving the Varilrix vaccine. The patient died several days later as a result of complications from encephalitis. As a precaution, the Polish medicines agency has suspended the distribution of vaccines from the batch in question. Belgium did not receive vaccines of this specific batch.
These vaccines are widely used across the EU, and encephalitis is listed as a side effect in their product information based on rare reports during post-marketing surveillance.
The committee will now assess all available evidence in order to better understand the risk of encephalitis and to determine if any regulatory action is necessary.
While the EMA is investigating the issue, the vaccines can continue to be used in accordance with the approved product information.
More information is available on the EMA website.