Jelmer is an internist specialized in acute medicine. He works at the Erasmus University Medical Center. He is the director of the acute medicine residency program, head of the section acute medicine of the department of Internal Medicine and secretary of the section Acute Medicine of the Dutch Society of Internal Medicine, and a member of iMERR. In 2019 he successfully defended his PhD-thesis titled “Prediction of the severity of illness and outcomes in the emergency department”. With his research he aims to improve patient care in the emergency department. Within iMERR he collaborates on research that focusses on cognitive error, bias and medical decision making.