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.

[10] During this time, Marrazzo was elected a Fellow of the Infectious Disease Society of America and Bennett Lorber Visiting Professor at Temple University.

The study was a randomized, placebo-controlled trial which examined the effects of daily use of oral tenofovir disoproxil fumarate had on over 5,000 women from 15 sites in South Africa, Uganda and Zimbabwe.

[11] 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.

[17] 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.