After graduation, Alexis held a series of jobs in academia. He was an assistant professor of chemistry at the State University of Haiti from 1973 to 1976 and a teaching and research assistant at Université Laval, Quebec, Canada, from 1977 to 1978, earning his master of science degree in food science and technology from Université Laval in 1979. He was then a professor of food technology and post-harvest technology at the State University of Haiti (1979–1987), a professor of post-harvest technology and human nutrition at Ecole Moyenne d’Agriculture (1979–1985), and Dean of the Faculty of Agronomy and Veterinary Medicine at the State University of Haiti (1985–1987). Between 1987 and 1990, he coordinated the founding of Quisqueya University, where he served as the school's first rector from 1990 to 1995.