TBE cases in Sweden have tripled over ten years despite rising vaccinations. Åke Lundkvist, professor of virology at Uppsala University, suspects the virus may have changed, reducing vaccine effectiveness. Researchers are now analyzing 12,000 ticks to investigate.
The number of reported TBE cases in Sweden has risen sharply over the past ten years. According to Folkhälsomyndigheten, cases increased from 238 in 2016 to 504 in 2025, with peaks like 595 in 2023 and a low of 274 in 2020. Vaccinations have risen at a similar pace.
Åke Lundkvist, professor of virology at Uppsala University, describes the trend as suspicious. "Something is fishy," he told SVT Nyheter. He suggests the vaccine may be losing effectiveness if the TBE virus has mutated. "The vaccine can become less effective if the virus causing the infection changes," Lundkvist explained.
To clarify, around 12,000 ticks collected by the Swedish public are being sent to Statens veterinärmedicinska anstalt (SVA). They will be analyzed in collaboration with Uppsala University's Zoonoscentret to compare current virus strains with those from previous years and the basis for existing vaccines.
Lundkvist stresses the need for vaccination. "Absolutely not [skip getting vaccinated], the vaccine works and it is the only important remedy we have today. We will find out if it can be even better," he said. The research aims to rule out other causes for the rise.
