Infection risk in sexual contacts of syphilis: A systematic review and meta-analysis

Objectives: Current guidelines recommend offering epidemiological treatment to asymptomatic contacts of early syphilis. This is on the expectation that up to 60% of sexual contacts of patients with syphilis will be infected. However, the evidence for this figure is sparse. We performed a systematic review and meta-analysis, to estimate the proportion of sexual contacts of syphilis that are infected with syphilis.

Methods: Two electronic databases (Medline and Embase) were reviewed in March 2021, to identify studies that reported rates of infection in sexual contacts of syphilis.

Results: Of 3,051 Embase and 1,828 Medline articles identified, 32 were included in the meta-analysis. In total 36,397 contacts were tested. The proportion of contacts infected varied across the studies, ranging from 10.7% to 97.5%, resulting in considerable heterogeneity (I²=98.5%). Pooling the studies gave an estimated proportion of infected contacts of 32.6% (95% confidence interval: 26.2% - 39.7%).

Conclusions: The risk of infection in sexual contacts of syphilis reported in the literature is highly variable, with a pooled estimate of 32.6%. This will help guide decisions regarding epidemiological treatment of sexual contacts of patients with syphilis. These decisions are increasingly important in this era of antibiotic resistance, with increasing emphasis being placed on antimicrobial stewardship.