Katherine O'Brien

In January 2019, O'Brien became the director of the Immunization, Vaccines and Biologicals Department at the World Health Organization (WHO). In this role, she is responsible for leading the overall work and strategy of the Department to advance the vision of reducing the health, social and economic burden of vaccine preventable diseases. The Director works across all levels of WHO (country, region and headquarters) in collaboration with partners to deliver country impact.

In July 1998, O'Brien joined the faculty of Johns Hopkins Bloomberg School of Public Health, eventually becoming a Professor of International Health and Epidemiology and Executive Director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health. Her scientific and policy work domestically and globally has focused on vaccine preventable illnesses, among both children and adults. The work has included surveillance, epidemiology, and vaccine clinical trials of pneumococcal disease; rotavirus; Haemophilus influenzae type b; respiratory syncytial virus and influenza vaccines. She has worked extensively with American Indian populations and in Africa and south Asia, partnering with local scientists and country program staff to develop rigorous scientific evidence and bring it into the vaccine policy arena, thereby accelerating the use and access to life-saving vaccines for children living in low resource countries and settings. She left Johns Hopkins in December 2018.

In 1996, as part of her job at the CDC, and given her previous experience in Haiti, O'Brien traveled to Haiti to investigate an outbreak of children who were dying. O'Brien and colleague Joel Selanikio (from the CDC) discovered the children had been exposed to liquid acetaminophen Afebril and Valodon manufactured by Pharval that was contaminated with almost 25% diethylene glycol (DEG), a poison. It was later discovered that there was contamination in the supply chain tracing back to a Chinese manufacturer.

From 1995 to 1997, she worked at the Centers for Disease Control and Prevention (CDC) as an Epidemiologic Intelligence Officer in the Bacterial Respiratory Diseases Branch.

In 1991, O'Brien worked for a year in Port-au-Prince, Haiti on a children's health project on HIV transmission. She said the experience was formative, and led her to view vaccines as being a social justice issue.

In 1984, O'Brien earned a BSc in chemistry from the University of Toronto. In 1988, O'Brien received an MD from McGill University at the age of 25 years old. O'Brien came to the United States to do her residency in pediatric at Johns Hopkins Hospital from 1988 to 1991. In 1994, O'Brien received an MPH from Johns Hopkins Bloomberg School of Public Health focused on International Public Health/International Health while also doing a two-year training program in pediatric infectious diseases.

O'Brien was born in Edmonton, Alberta. She grew up in Ottawa, in the province of Ontario, and graduated from Lisgar Collegiate Institute in 1980.

Katherine "Kate" L. O'Brien (born 1963) is a Canadian American pediatric infectious disease physician, epidemiologist, and vaccinologist who specializes in the areas of pneumococcal epidemiology, pneumococcal vaccine trials and impact studies, and surveillance for pneumococcal disease. She is also known as an expert in infectious diseases (including pneumonia and diarrheal diseases) in American Indian populations. O’Brien is currently the Director of the World Health Organization's Department of Immunization, Vaccines and Biologicals.