The City Airport Train (CAT) runs every half hour between the airport and Landstraße / Wien Mitte, the journey takes 16 minutes (one way € 12,00/ return ticket € 21,00). Boarding pass purchase in Wien Mitte possible (3rd, Invalidenstraße / Marxer Brücke) - on its own CAT platform.
If you opt for public transport go on like this:
To Garnisongasse 7 (AIHTA) take subway line 3 (U3) to Volkstheater and from there subway line 2 (U2) to the town hall (exit Rathaus). Now you are just a few minutes walk from Garnisongasse 7.
HTA Austria - Austrian Institute for Health Technology Assessment GmbH