The vaccine against Poliomyelitis is mandatory.
By the age of 8 weeks it is normal to start the vaccination against: polio, diphtheria, tetanus, pertussis (whooping cough), meningitis, hepatitis B, pneumonia, and pneumococcal infection.
By the age of 1 it is recommended to start the vaccination against measles, mumps, and rubella (German measles).
By the age of 13/15 months it is recommended to start the vaccination against meningitis C.
Some of these vaccinations will need to be renewed later on and can be administered later on if needed.
A time schedule of the most common vaccines:
http://www.kindengezin.be/img/oktober2015vaccinatieschema.pdf