Treatment Completion With Three-Dose Series of Benzathine Penicillin Among People Diagnosed With Late Latent and Unknown Duration Syphilis, Maricopa County, Arizona

Background: Syphilis is a public health concern as cases are rising each year. If untreated, syphilis is associated with significant morbidity and risk of vertical transmission during pregnancy. For people with late latent and unknown duration stages, 3 injections of benzathine penicillin G (BPG) at 1-week intervals are recommended. Our study quantified treatment for people diagnosed with late latent and unknown duration syphilis in Maricopa County, Arizona with a secondary analysis of pregnant women to assess completion of 3 injections of BPG in multiple time intervals.

Methods: Maricopa County syphilis case data were extracted from the state-run database (PRISM). Records were reviewed for people with late latent and unknown duration syphilis during January 1, 2016, to December 31, 2021. Treatment types and time intervals between treatments were analyzed.

Results: Of a total of 14,924 people with syphilis reported in Maricopa County, 5372 (36.0%) were staged as late latent or unknown duration syphilis. Completion of 3 BPG injections in the time frame of 7 to 9 days was 42.9% (n = 2302). Completion among pregnant women (n = 406) with 3 injections was 68.7% (n = 279).

Conclusions: The completion rate of 3 BPG injections for people with late latent or unknown duration syphilis is low. An unmet need exists to identify barriers to treatment including access to BPG and public health follow-up after the first injection. Prioritized effort is needed to identify and classify patients as having earlier stages of syphilis that require only 1 BPG injection.