Scenario projections of congenital syphilis incidence in California, 2025-2030

BackgroundIn 2022, the yearly rate of congenital syphilis (CS) cases in California reached its highest point since 1950. We explored how different prevention strategies in California could impact future CS case incidence. MethodsScenario modeling was used to project CS incidence from 2025 through 2030 based on 2015-2024 surveillance data. We compared a baseline scenario with scenarios that modeled 1) changes in the rate of annual female syphilis cases; and 2) changes in the proportion of pregnant persons adequately treated for syphilis. We then used 2016-2023 hospitalization discharge data from California to estimate charges associated with treatment of a CS case. ResultsA 5-50% reduction in the absolute rate of female syphilis cases led to a 3-30% decrease in cumulative CS cases during the projection period. Increasing the proportion of pregnant persons adequately treated for syphilis by 5-50% led to a 2-23% decrease; combining both scenarios resulted in a 4-45% reduction. In the baseline scenario, projected CS treatment-associated hospitalization charges were estimated to total $399 million. A 45% reduction in CS cases resulting from the combined interventions would reduce charges by $158 million. DiscussionFemale syphilis incidence and adequate treatment during pregnancy have substantial impact on CS case incidence and associated charges. California has implemented universal syphilis screening guidelines for all people aged 15-49 years alongside interventions supporting testing and treatment of pregnant persons. Continued implementation of these interventions will result in considerable savings around CS treatment and reduced need for management of long-term sequelae.