Pre-exposure prophylaxis (PrEP) for HIV, based mainly on the use of tenofovir and emtricitabine, has proven highly effective in reducing viral transmission when used correctly. However, its protective action does not extend to other sexually transmitted infections (STIs) such as syphilis, gonorrhea, chlamydia, and herpes. An increase in STI incidence has been observed among PrEP users, possibly associated with higher-risk behaviors due to a perceived sense of protection against HIV. This study evaluated the incidence of STIs in populations using PrEP, identifying epidemiological patterns and factors associated with breakthrough cases. A systematic search was conducted in the PubMed, Scopus, and Web of Science databases using the terms “PrEP AND STI incidence,” “PrEP AND breakthrough infections,” and “HIV prevention AND STI risk.” Observational studies and clinical trials published between 2019 and 2024 that reported data on STIs in PrEP users were included. Statistical analysis was performed using RevMan 5.4 software, with calculation of odds ratios (OR) and 95% confidence intervals (CI). Of the 1,235 articles identified, 18 met the inclusion criteria. The analysis revealed a high prevalence of STIs among PrEP users, with cumulative incidence ranging from 25% to 50% across different cohorts. Gonorrhea was the most frequent STI (30–45%), followed by chlamydia (20–35%) and syphilis (5–15%). Two studies reported a significant association between PrEP use and increased risk behaviors, such as reduced consistent condom use (OR: 2.1; 95% CI: 1.5–2.9). In addition, PrEP users were more likely to experience STI reinfection within 12 months (OR: 1.8; 95% CI: 1.3–2.5). Despite the proven effectiveness of PrEP in preventing HIV, its use is associated with a higher incidence of other STIs, possibly driven by behavioral changes. Combined strategies, such as health education, frequent STI screening, and promotion of condom use, are essential to mitigate this effect.
Letizia Pires Marchelli (Sun,) studied this question.