As health expenses are very high in Germany, your Schengen health insurance will take care of any unforeseen medical incidents or accidents that might occur to you during your stay. Your health insurance must feature on the list of Schengen approved insurance companies and policies. A travel health insurance bought in Germany by the host or organisation is also acceptable as long as it fulfills the Schengen requirements.
If you apply for a multiple entry visa valid for a year or longer, a health insurance policy does need to be presented for the first trip only. However, you are obligated to have adequate coverage for any subsequent trip to the territory of the Schengen member states.