Only the vaccination against poliomyelitis is legally obligatory in Belgium. After your child has received the last dose (usually at 15 months but later if needed), you will receive a certificate, which you will need to submit to the commune as soon as possible. Other vaccinations are normally received and administered by the health authorities of the country.
These are the vaccins that children usually get in Belgium: http://www.vaccination-info.be/assets/files/Doc_ONE/rdv_vaccins_2016.pdf