by Carolyn Chu, MD, MSc, AAHIVS, AAHIVM Chief Medical Officer
June 20, 2023
Johnson KA, Burghardt NO, Snyder RE, et. al. Comparing 7 vs. 6-8 day penicillin treatment intervals among pregnant people with syphilis of late or unknown duration: no difference found in incidence of congenital syphilis. Open Forum Inf Dis. 2023 Jun 8. Online ahead of print. https://doi.org/10.1093/ofid/ofad300
This analysis of California STI surveillance data aimed to determine whether infants born to birthing parents with syphilis of late/unknown duration treated with 3 weekly doses of benzathine penicillin G (BPGx3) administered at 6-8 day intervals (initiated ≥ 30 days before delivery) would be more likely to meet congenital syphilis (CS) criteria than infants born to parents who received BPGx3 at strict 7-day intervals. CS cases were defined using a combination of surveillance and clinical criteria. Between January 2016 and June 2019, 1,092 parent-infant dyads were eligible for analysis. 607 parents (55.6%) received BPGx3 at strict 7-day intervals, 70 (6.4%) received treatment at 6-8 day intervals, and 415 (38%) received no or inadequate treatment. There were no significant differences between parents receiving 7 vs. 6-8 day interval BPGx3 with regard to age, race/ethnicity, HIV status, receipt of prenatal care, trimester for establishing prenatal care, and highest non-treponemal titers in pregnancy. Parents who received no/inadequate treatment were less likely to have received prenatal care and were diagnosed with syphilis later in pregnancy, and almost 60% had not received any treatment prior to delivery. CS incidence proportions in the 7, 6-8 day, and no/inadequate treatment groups were 5.6%, 5.7%, and 36.9% respectively: there was no difference in CS incidence between the first two groups.
Despite a relatively small population involved in this retrospective analysis, these results suggest that 6-8 day intervals of benzathine penicillin G for prenatal treatment of syphilis of late/unknown duration may potentially be sufficient. As authors note, having a small window of flexibility for indicating whether an intervention provides adequate CS prevention may translate into very meaningful impact in clinical and public health practice. More studies including larger sample sizes and detailed case information would help potentially replicate and/or expand upon this study’s findings.
Disclaimer: Although employed at the same institution as the study’s lead author, Dr. Chu was not involved in this research.
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