Marrazzo joined the faculty at the
University of Washington School of Medicine in 1995. While there, she co-founded the Lesbian/Bisexual Women’s Health Study with nurse practitioner Kathleen Stine after noticing an unusual number of middle-aged women had abnormal Pap smears. The results of their findings secured them funding from the
National Institute of Allergy and Infectious Diseases (NIAID) to investigate the prevalence and routes of transmission of various STDs among lesbian and bisexual women. This led to a co-authored study titled
Pap Smear Screening and Prevalence of Genital Human Papillomavirus Infection in Women Who Have Sex with Women, which found that out of 300 women in the Seattle area, 13 percent tested positive for HPV and 4 percent had pre-cancerous changes on a Pap test. The following year, she was elected a Fellow of the
American College of Physicians. In 2008, Marrazzo was appointed a member of the Subspecialty Board on Infectious Disease by the
American Board of Internal Medicine (ABIM), and four years later was named its chair. During this time, Marrazzo was elected a Fellow of the
Infectious Disease Society of America and Bennett Lorber Visiting Professor at
Temple University. The final published paper failed to prove that oral pre-exposure prophylaxis (PrEP) or of a tenofovir-containing vaginal microbicide gel was effective in lowering the risk of HIV. Considered an expert in the field of HIV prevention, Marrazzo was appointed a co-chair of an interdisciplinary panel of experts to create a guideline in achieving an AIDS-free generation. The guidelines, which were later published in the
Journal of the American Medical Association, integrated evidence-based behavioral interventions for people with HIV or at high risk for HIV infection. Her efforts in HIV prevention earned her the 2015 American Sexually Transmitted Diseases Association (ASTDA) Achievement Award and appointment to chair of the American Board of Internal Medicine Council. In 2016, Marrazzo succeeded Edward W. Hook, III as director of the
University of Alabama School of Medicine Division of Infectious Diseases. After stepping down as president of the International Society for STD Research, she was named to the Infectious Diseases Society of America board of directors. On October 23, 2019, she was named principal investigator of a three-year $3.5 million grant study from NIAID to test the effectiveness of the
Bexsero vaccine in protecting vulnerable populations from gonorrhea. During the
COVID-19 pandemic, Marrazzo studied whether blood clots could result in the spread of the virus through the human body. She also oversaw clinical trials of
remdesivir as a treatment against
COVID-19 at the
University of Alabama at Birmingham. In August 2023, Marrazzo was named director of NIH’s
National Institute of Allergy and Infectious Diseases (NIAID), succeeding acting director
Hugh Auchincloss. As a lesbian, she is one of the first members of the
LGBT community to hold the position. She was elected a Member of the
National Academy of Medicine in 2024. On March 31 during the
2025 United States federal mass layoffs, Marrazzo was placed on
administrative leave at NIAID and offered a position at the
Indian Health Service. On September 4, she joined a
whistleblower complaint against research grant cancellations. Secretary of Health Robert F. Kennedy Jr. terminated Marrazzo’s employment at NIAID, in a letter dated 26 September 2025. == Selected publications ==