After this period at the latest, the fourth trick would have to be set as a refreshment. At least that’s what the Ministry of Health’s vaccination dashboard currently calculates. Explained using a fictitious example: Anyone who got the first two vaccinations from Biontech / Pfizer in April and May and then carried out the booster on December 1st with the same vaccine will be informed that their vaccination certificate is only up to August 28, 2022 is valid. Accordingly, you would need the fourth dose around nine months after the third stitch in order to continue to have a valid green passport. Officially, there are no government regulations yet.