Asgeir Johannessen completed his medical degree in Norway in 2000. He is a specialist in internal medicine and infectious diseases. In 2011 he defended his PhD at the University of Oslo which focused on simplification of HIV treatment in sub-Saharan Africa.
In 2015, he established a hepatitis B treatment program in Ethiopia, one of the largest treatment centres on the continent. He has been the primary supervisor of 3 PhD students in this project, who all defended their theses in 2019-2020. From 2021, he has led the expansion of this program, aiming for simplification and improved access to HBV therapy in the country.
He has published more than 40 peer-reviewed scientific papers and was deemed professor competent in infectious diseases and global health in 2020. He currently works as an infectious diseases consultant at Tønsberg Hospital and Deputy Director at the Centre for Global Health, University of Oslo.