Manuel M. Dayrit was Secretary of Health (Minister) of the Philippines from 2001 to 2005 when the Department of Health (DOH) was recognized for its effective implementation of disease control programs (including for SARS, dengue, tuberculosis, and vaccine-derived polio); the implementation of the health sector reform agenda which included widening the use of generic medicines; and the broadening of access to social insurance (PhilHealth) by indigents. Under his leadership, the DOH was cited among the top-performing government agencies.

From 2005 to 2012, he was Director of the Department of Human Resources for Health at the World Health Organization (WHO) in Geneva. The WHO Code on the International Recruitment of Health Personnel was developed during this time and adopted by Member States at the World Health Assembly in May 2010. Prior to this appointment, he was a member of the Commission on Social Determinants of the World Health Organization.

He was the founding Director of the Philippines Field Epidemiology Training Program and directed it from 1986 to 1997. For work in the control of AIDS, cholera, and Red Tide, he was named an Outstanding Young Scientist by the National Academy of Science and Technology in 1990. In 2006, Dr. Dayrit became an Honorary Fellow of the London School of Hygiene and Tropical Medicine. In 2008, he was the Centennial Awardee for Health of the Alumni Association of the University of the Philippines.

Dr. Dayrit has degrees from the Ateneo de Manila University (AB, 1972; honorable mention); the University of the Philippines College of Medicine (MD, 1976); and the London School of Hygiene and Tropical Medicine (MSc with distinction, 1982; British Council Scholar). His current research work is on health care at primary level. Recent scientific contributions were published in 2018 by the WHO Asia-Pacific Observatory on Health Systems and Policies including: 1) The Philippine Health System Review 2^nd edition (lead author) and 2) Resilient and People-centered health systems: Progress, challenges and future directions in Asia (lead author for the chapter on the Philippines).