John D. Clemens

Professor John Clemens is an infectious disease epidemiologist with over 30 years of experience designing, conducting, and analyzing large population-based epidemiologic studies and vaccine field trials in low-income countries, as well as developing new methodologies for the clinical evaluation of vaccines. He is a graduate of Stanford (B.S.) and Yale (M.D.).

From 1983 to 1988, he served as a research scientist at the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), where he led the first efficacy trial of an oral vaccine against cholera. After returning to the United States, he held senior positions at the University of Maryland and the National Institutes of Health.

In 1999, he became the first Director-General of the International Vaccine Institute (IVI) in Korea, where he led the team that developed a killed oral cholera vaccine (Shanchol). This vaccine achieved WHO prequalification in 2010 and was the first oral cholera vaccine to be included in the global oral cholera vaccine stockpile.

In 2011, he moved to UCLA as Professor of Epidemiology and Founding Director of a new Center for Global Infectious Diseases. From 2013 to 2021, Dr. Clemens served as Executive Director of the International Centre for Diarrhoeal Disease Research, Bangladesh (icddrb). Since 2021, he has worked as Senior Scientific Advisor to the Director-General of the International Vaccine Institute in Seoul.

Dr. Clemens is the author of over 500 peer-reviewed publications. He received the 2010 Sabin Gold Medal and was co-recipient (with Jan Holmgren) of the 2018 Prince Mahidol Award in Public Health.

The Work:

John Clemens, an epidemiologist, and Jan Holmgren, an immunologist, have worked together for over 40 years to transform global cholera control by creating oral cholera vaccines made from inactivated, or killed, bacteria that are safe, effective, and affordable. Their work spans laboratory research, vaccine development, clinical trials, and public health programs. 

Holmgren’s fundamental research showed how cholera causes disease and how immunity develops, demonstrated that oral vaccines provide strong protection, identified the components needed for effective immunity, enabling him to develop Dukoral, the world’s first oral cholera vaccine to be internationally licensed and WHO-prequalified.

Building on Holmgren’s discoveries and vaccine development, Clemens led large field trials in cholera-affected communities, beginning at the International Centre for Diarrhoeal Diseases Research, Bangladesh. The studies, which led to the licensure of Dukoral, showed that the oral cholera vaccines were safe, offered lasting protection, and reduced transmission in the wider community, while also introducing methods to measure vaccine impact under real-world conditions.

To reach those most at risk in low-income settings, they also worked with Vietnamese and Indian manufacturers to develop Shanchol, the first affordable, WHO-prequalified oral cholera vaccine, whose introduction into public health practice was supported by Clemens’ research showing it was practical, widely accepted, and effective for large-scale use.

The Impact:

Cholera is a severe diarrheal disease that can spread quickly in communities without access to clean water and proper sanitation, causing thousands of deaths each year. The work of Drs. Clemens and Holmgren has transformed how the disease is prevented and controlled. Their research provided the evidence that led the WHO to recommend oral cholera vaccines for both ongoing outbreaks and areas where cholera is common, and it supported the creation of the world’s first global oral cholera vaccine stockpile.

Since the stockpile was established, millions of vaccine doses have been distributed through national programs and emergency responses. These vaccines have been safe, effective, and able to reduce transmission in entire communities. Their work has led to large declines in cholera cases and continues to protect and save lives around the world.