office of professional development & engagement

Preventive Medicine Residency Program

2025–26 Residents

Andrea Leung, MD, FACOG

Dr. Andrea Leung is a first-year resident in the CDPH Preventive Medicine Residency Program. She completed her medical degree at Thomas Jefferson University, followed by her residency in obstetrics and gynecology at Jefferson Einstein Philadelphia. Due to her interest in working with underserved communities, she completed a global health fellowship in Malawi, where she was recognized as a Massachusetts General Hospital Fellow in Global Clinical Education. Following her training, she practiced obstetrics and gynecology at Kaiser Permanente for three years. Her desire to leave a greater impact at a population level led her to pursue a residency in public health. She is currently completing her MPH at the University of California Davis and will be working in the Sacramento County Sexual Health Clinic. She plans to complete her practicum with the Sacramento County Department of Health Services, focusing on prenatal substance use and mental health disorders.

Picture of PMRP resident

Antonio Chahine, MD, MSPH

Dr. Antonio Chahine is a second-year resident in the California Department of Public Health Preventive Medicine Residency Program. Originally from Caracas, Venezuela, he completed his B.S. in Biochemistry and a Master of Science in Public Health with a concentration in Epidemiology at the University of Miami, where his early work focused on HIV prevention, mental health equity, and the expansion of mobile testing and PrEP services. He later earned his medical degree from Stanford University, where he led a community health needs assessment addressing the needs of Latinx families receiving care at Lucile Packard Children’s Hospital and completed a full year of clinical training in Pediatrics at Stanford Hospital.

As a Preventive Medicine resident, Dr. Chahine has contributed to projects spanning outbreak preparedness, vaccine accessibility, and infectious disease surveillance. His quality improvement work supported efforts to analyze pediatric immunization service patterns at the Adult Immunization & Travel Clinic, generating findings to inform future planning. He also collaborated on Shigella prevention messaging, helping produce communication materials and digital assets under the guidance of local communicable disease leadership. Moreover, Dr. Chahine played an active role in One Health coordination for H5N1 preparedness, working with both local and state agencies to strengthen environmental health response protocols.

Dr. Chahine has received formal training in STI diagnosis, management, and prevention, with direct clinical experience at San Francisco City Clinic and Zuckerberg San Francisco General Hospital. He is currently contributing to research on HIV prevention in the Bay Area, reflecting his continued commitment to health equity and community-responsive epidemiology.

In addition to formal coursework, Dr. Chahine has several years of experience as a clinical research coordinator, contributing to multi-site studies and multiple peer-reviewed publications focused on HIV and mental health. He has also served as a teaching assistant in epidemiology, biostatistics, and clinical medicine at both Stanford and the University of Miami and remains deeply engaged in mentoring first-generation students pursuing careers in medicine and public health.

Brad Johnson, MD, MPH

Brady "Brad" Johnson, MD, MPHTM is a first-year resident in the CDPH Preventive Medicine Residency Program. He earned a Bachelor of Science in Neuroscience from Tulane University, where he later returned to complete both his Doctor of Medicine and Master of Public Health and Tropical Medicine. He completed his internship in Pediatrics at UCSF Benioff Children’s Hospital Oakland.

Brad is a passionate advocate for preventative medicine, health equity, and public health innovation. His work has focused on harm reduction, LGBTQ+ sexual health, and digital health interventions. His scholarly contributions have been published in the American Journal of Public Health and the American Journal of Addiction, and he has presented at national conferences and to federal agencies including the CDC.

During the COVID-19 pandemic, Brad played a central role in modernizing contact tracing infrastructure at the San Francisco Department of Public Health. He helped design and implement California’s Virtual Assistant (VA), an AI-driven chatbot that significantly increased the state’s capacity to conduct COVID-19 case investigation and contact tracing. The chatbot enabled rapid outreach to confirmed COVID-19 cases and prioritized phone calls for high-risk and vulnerable populations. He developed real-time reports and dashboards to analyze responses, supported training and rollout efforts, and co-authored research that shaped public health policy during critical phases of the pandemic. His work was recognized at both local and national levels, and helped inform broader digital public health strategies.

Prior to medical training, he worked as a healthcare technology consultant and Epic analyst, developing clinical workflows and implementing large-scale EHR systems. He brings this systems-level thinking to his current work in clinical care, public health research, and policy.

Currently, Brad works within the COVID Control Branch of CDPH, contributing to the CDC’s Data Modernization Initiative—a nationwide effort to enhance the timeliness, interoperability, and actionability of public health data systems. He also practices clinically at San Francisco City Clinic, a sexual health and STI specialty clinic serving diverse and underserved populations. This dual role allows him to integrate frontline clinical insight with population-level public health impact.

Outside of medicine, Brad is an avid world traveler, certified Rescue Scuba Diver, and vocal advocate for LGBTQ+ health and harm reduction. He has visited more than 45 countries, and finds grounding through meditation and melodic house music.

Patrick Nguyen, MD

Dr. Nguyen is a first-year resident in the California Department of Public Health (CDPH) Preventive Medicine Residency Program. He holds a Bachelor of Science in Pharmaceutical Sciences from Ohio State University and earned his medical degree from Thomas Jefferson University’s Sidney Kimmel Medical College. He completed his internship in Anesthesiology at Geisinger Medical Center. Throughout his academic and professional career, Dr. Nguyen has actively sought opportunities to improve healthcare access for underserved populations, especially immigrant communities. He has partnered with multiple organizations to deliver medical and dental care both in the U.S. and abroad. His passion for teaching and advocacy has driven his work with homeless and housing-insecure communities, where he has focused on health education and outreach. Dr. Nguyen is pursuing a Master of Public Health (MPH) at the University of California, Berkeley. He is also gaining clinical experience in Napa County, where he remains committed to community-centered, equitable healthcare—with a particular focus on chronic disease prevention and substance use disorder.

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