No special vaccinations are required for travel to Macedonia and there are no unusual health concerns. It is always a good idea to have a tetanus jab before travelling.
The biggest concern is widespread shortages of medicines; ensure you take out adequate travel and medical insurance in case you have to pay through the nose for medical supplies should you fall ill while in Macedonia.
The country is relatively bug-free; mosquitoes can be an issue in Ohrid in July and August, and at Canyon Matka in the evening.
Tap water is generally safe to drink in Macedonia (you'll see plenty of public fountains around Skopje and in rural villages), but check with locals before filling up your water bottle, just to be on the safe side.