For technical reasons, the digital vaccination certificate expires after 365 days, regardless of the medical validity. After that, the QR code can no longer be read. Users of the Corona warning app are informed 28 days before expiration and are given the opportunity to update the certificate. If no update is offered, the certificate is still current. In principle, the certificate can be renewed 90 days after expiration of the technical validity itself. This also applies to convalescent certificates. Details are provided by the federal government.