The European Union will recommend to limit the validity of vaccine certificates for 9 months, thereby bringing travelers to be vaccinated more often. This is reported by Bloomberg with reference to sources.
The European Commission (EC) will announce this later today, November 25th. It is assumed that the EC will also make sure that from January 10, 2022, the association member countries opened for travelers who have a vaccine approved by the World Health Organization.
Although COVID certificates are also issued by the fact that he got pneumonia, the EC plans to insist on another change in the rules of entry: the priority wants to give precisely travelers. For the sake of entry into the EU territory, they will need to be revaccination every 9 months.