Trends in RPR Seropositivity among Children Younger than 2 Years in South Africa, 2010-2019.

A positive rapid plasma reagin (RPR) result in children under the age of 2 years indicates either passive transplacental transfer of maternal antibodies or active infection with syphilis (possible congenital syphilis). We describe trends in RPR seropositivity in this population using centralized laboratory data. A secondary analysis of laboratory data collected through the National Health Laboratory Service, Corporate Data Warehouse from 2010 to 2019 was conducted. Of the 127 150 children <2 years included in the analysis, 10 969 [8.6%; 95% confidence interval (95% CI) 85-88]) were RPR seropositive. RPR seropositivity increased from 6.5% to 13.0% between 2010 and 2019. Overall, the annual rate of RPR seropositivity was relatively stable between 2010 and 2018 with a range of 89-127/100 000 live births, increasing sharply to 165/100 000 livebirths in 2019. KwaZulu-Natal and North West provinces recorded the largest increases in annual seropositivity rate, while Eastern Cape and Western Cape had the most significant declines. Although this analysis is limited to laboratory results, in the absence of major changes in testing practices, there may be a rise in the burden of antenatal syphilis exposure in utero indicating an increase in maternal syphilis and syphilis transmission in the general population. South Africa needs to intensify Mother-to-Child Transmission of syphilis elimination efforts to reach the WHO target of ≤50 cases per 100 live births by 2030.