Вот тут пишут что Е106 не обязательна, если есть EHIC.

A student, researcher or trainee abroad

If you go to another EU country for your studies, research work, a work placement or vocational training, you must have comprehensive health insurance in your host country.

• If you are not employed, the European Health Insurance Card (EHIC) could be an option, if you are eligible.
• If you are employed in your host country, you will need to subscribe to a local healthcare scheme there.
  Some PhD students may be considered resident workers and can be required to subscribe to the local healthcare scheme or take out private insurance.
• If you are sent for a temporary period to a university or research institution in another EU country by your university or research institute of origin, then you will remain under your home healthcare scheme for the time you are posted. You should apply for the EHIC card, or for an S1 form(formerly the E 106), before leaving.

Check with your health insurance provider or with the National Contact Point in your home country whether they will cover the cost of your healthcare abroad for the full duration of your stay. If they do, administrative procedures can be simpler if you have a valid European Health Insurance Card (EHIC).

Some national health insurers will however only cover the costs of your healthcare in another country for a limited time; this is often the case for mature students (older than 28 or 30) and workers on training abroad. If this is the case for you, you will need to register for state healthcare in your host country or to take out private health insurance.