Model variables and sources.

aWe assumed no prevalent infection at baseline.bEarly neurosyphilis refers to neurosyphilis that develops during the primary, secondary, or early latent stages of syphilis infection.cEarly syphilis refers to primary, secondary, or early latent syphilis infection.dBase case treatment cost for neurosyphilis was calculated as the weighted average of inpatient and outpatient treatment, assuming 95% of cases require inpatient treatment. Base case treatment cost for tertiary syphilis was calculated as the weighted average of gummatous and cardiovascular syphilis, assuming 62% of tertiary syphilis cases are gummatous and 38% are cardiovascular [16]. Cardiovascular cases were further subdivided into those requiring surgery (20%) [70] and those not requiring surgery.ePost-dural headache was assumed to require a general practitioner visit. Anaphylaxis was assumed to require hospitalization.