From 2011 to 2017, Hans was Professor of Global Health at the University of Groningen. From 2008 to 2011, he was WHO Director for Essential Medicines and Pharmaceutical Policies, and from 2004 to 2008, WHO Director of Medicine Policies and Standards. Hans has advised over 60 Low- and Middle Income countries on their national pharmaceutical policies. He edited many normative WHO publications and has published over 80 scientific papers on essential medicines, including many in The Lancet and the British Medical Journal. He is a co-founder and former chairman of the UN Interagency Pharmaceutical Coordination Group, which coordinates the pharmaceutical policies of UN agencies dealing with pharmaceuticals (e.g., WHO, UNICEF, UNFPA, UNAIDS, the World Bank, the Global Fund and UNITAID). Hans is qualified as a medical doctor and has received a PhD in Public Health as well as an honorary Doctorate of Science. Before joining WHO in 1985, Hans worked as a mission doctor in India and Ghana for five years.