About Us

Dr. John Redd is an internist and medical epidemiologist with more than three decades  of experience in public health, most recently as a medical officer with the U.S. Department of Health and Human Services (HHS).

He began his federal career as a clinical internist with the U.S. Indian Health Service (IHS) in Shiprock, New Mexico. Following two years of training with the Centers for Disease Control’s Epidemic Intelligence Service, he served in epidemiology and clinical positions with CDC, IHS and HHS Headquarters, where he was chief medical officer for the Assistant Secretary for Preparedness and Response. He held national epidemiology leadership positions during the H1N1 pandemic and the West African Ebola response, spending over a year deployed in Sierra Leone. During the COVID-19 response he directed the Federal Healthcare Resilience Task Force, directed national allocation and distribution of new therapeutics, including remdesivir and monoclonal antibodies, and led field response teams in California and Japan.



He received the Public Health Service Meritorious Service Medal and the State Department Superior Honor Award for his Ebola service in Sierra Leone. For his service during the COVID-19 response, he received the United States Public Health Service Distinguished Service Medal, the service’s highest award. 

Dr. Redd received his bachelor’s degree from Harvard College and his medical degree from the University of Texas Southwestern Medical School in Dallas. He then completed a residency in internal medicine at Columbia-Presbyterian Medical Center and earned a Master of Public Health in Epidemiology at Columbia University in New York. He was elected a fellow of the American College of Physicians in 2002 and was a 2010-2011 Public Health Leadership Institute Scholar. He is the co-author of over 90 publications.

Dr. Colin Shepard joined the Schmidt Initiative for Long Covid as its chief medical officer in September 2024. Prior to joining SILC, Dr. Shepard was a medical officer with the U.S. Centers for Disease Control and Prevention’s Office of Readiness and Response. He served as the agency’s liaison to the Office of the Administration for Strategic Preparedness and Response at the Department of Health and Human Services, where he supported the Covid therapeutics effort.

In addition to his efforts during Covid, Dr. Shepard’s career includes leadership roles at CDC in which he worked on viral hepatitis, HIV/AIDS and tuberculosis. His experience outside CDC includes serving as a medical officer in the U.S. Food and Drug Administration, directing HIV field services and epidemiology at the New York City Department of Health and Mental Hygiene, and monitoring and evaluating HIV response  at the International Training and Education Center on HIV-Ethiopia. 

He practices internal medicine at a clinic in Washington, D.C., serving uninsured and underinsured patients.

Dr. Shepard attended medical school at Wake Forest University and completed his residency in internal medicine at the University of Rochester/Strong Memorial Hospital.

Victoria Callahan began her professional career as an epidemiology fellow for the Peace Corps Chief Medical Officer, where she was responsible for surveillance and reporting on disease outbreaks in Peace Corps countries.

Prior to joining SILC, Victoria was the public health analyst to the chief medical officer in the Office of the Assistant Secretary of Preparedness and Response (ASPR) at the U.S. Department of Health and Human Services (HHS). During the COVID-19 pandemic, Victoria was on the ASPR COVID-19 therapeutics team responsible for the allocation, distribution and administration of life-saving monoclonal antibodies.

Victoria has also served as the direct aid to two presidential appointees and has extensive international experience—living, volunteering, studying and working in more than seven countries across four continents. Victoria has a bachelor’s degree from The George Washington University and is currently pursuing a Master of Public Health from Dartmouth College.

Adam Tewell joined the Schmidt Initiative for Long Covid in October 2024 after almost a decade at the U.S. Department of Health and Human Services (HHS). At HHS’s Administration for Strategic Preparedness and Response, he served in multiple roles coordinating international engagement, including U.S. International Health Regulations National Focal Point program manager, supporting the development of World Health Organization Emergency Use Listing procedures and building technical partnerships with his organization’s counterparts worldwide to strengthen global health resilience. During the Covid pandemic he led allocation and distribution of Covid therapeutics.  

Adam also served in HHS’ Office of Global Affairs and the U.S. Food and Drug Administration, focusing on international health engagement in the Asia Pacific region and with multilateral organizations. Outside of government, he has worked as a consultant for the World Bank and pharmaceutical and medical device organizations. 

He has a Master of Public Administration from Cornell University and a bachelor’s degree from Trinity College. He volunteers with nonprofit mental health organizations focusing on enabling individuals with mental health conditions to access housing and employment.