Here it says from the guide 0104, I just copied and paste it here.
Medical requirements
Do not undergo an immigration medical exam unless we advise you to do so. A medical exam will be required and you’ll will receive instructions after you submit your application.
All your family members who are not already Canadian citizens or permanent residents must undergo and pass an immigration medical exam, even if your family members will not be processed for permanent residence with your application. Family members who do not undergo and pass a medical exam will not be eligible to be sponsored at a later date. Your family members will be contacted by the visa office in their area with instructions on their medical exams.
Medical requirements
Do not undergo an immigration medical exam unless we advise you to do so. A medical exam will be required and you’ll will receive instructions after you submit your application.
All your family members who are not already Canadian citizens or permanent residents must undergo and pass an immigration medical exam, even if your family members will not be processed for permanent residence with your application. Family members who do not undergo and pass a medical exam will not be eligible to be sponsored at a later date. Your family members will be contacted by the visa office in their area with instructions on their medical exams.