On 1 February 2022, the decision of the European Commission (EC) that COVID-19 vaccination certificates are valid for 9 months from the primary vaccination for 16 years and older enters into force. The software that reads the certificates at the border will calculate the validity period based on the date of the last dose of the primary vaccination. If more than 9 months have passed since the primary vaccination, the certificate will be considered invalid at the border, no matter what it says.