For the 3rd dose (or the 2nd dose if you have received the Janssen/Johnson & Johnson vaccine), mRNA vaccines are recommended (BioNTech/Pfizer, Moderna), regardless of which vaccine was initially administered. The National Vaccination Board recommends the Spikevax (Moderna) vaccine for the basic immunisation for persons 30 years or older. Upon express request and in line with the approval, the Moderna vaccine can also be administered to persons under 30 years of age.
A heterologous vaccination schedule, i.e., switching between shots (1st, 2nd, and 3rd vaccine) is called “mix-and-match vaccination”. As this is not yet approved by the individual manufacturers, its application is off-label.