Refund liabilities - Narrative (Details) - EUR (€) € in Thousands |
6 Months Ended | 12 Months Ended | |
|---|---|---|---|
Jun. 30, 2026 |
Dec. 31, 2025 |
Dec. 31, 2024 |
|
| Disclosure of disaggregation of revenue from contracts with customers [line items] | |||
| Refunds provision | € 17,874 | € 17,498 | € 26,141 |
| Current refunds provision | 11,091 | 10,814 | |
| Additions, refund liability | 971 | 4,649 | |
| Non-current refunds provision | 6,783 | 6,684 | |
| Return provision and rebates | |||
| Disclosure of disaggregation of revenue from contracts with customers [line items] | |||
| Refunds provision | 1,200 | 1,800 | |
| Pfizer Inc. | Lyme VLA15 | Amended collaboration and license agreement | |||
| Disclosure of disaggregation of revenue from contracts with customers [line items] | |||
| Current refunds provision | 9,700 | 9,000 | |
| Additions, refund liability | 400 | 3,500 | |
| GSK | Supply agreement | |||
| Disclosure of disaggregation of revenue from contracts with customers [line items] | |||
| Refunds provision | 6,800 | 6,700 | |
| Non-current refunds provision | € 6,800 | € 6,700 |