This will depend on what vaccinations your teenager has had overseas and if you are able to provide valid records of their vaccination/s.
If the vaccination schedule of your home country differs greatly for the Australian Immunisation Schedule, or if valid records are not available for your teenager, then your healthcare practitioner or GP may recommend your teenager go through a catch-up schedule in order to be in line with the National Immunisation Program (NIP). People aged less than 20 years are eligible for free catch-up vaccinations.