How has antenatal care HIV and syphilis surveillance evolved, and what comes next?
Antenatal care (ANC) services provide convenient access to healthy women who are sexually active and can serve as a proxy for the general population with respect to HIV surveillance. Since 1990, South Africa has conducted antenatal care HIV and syphilis sentinel surveillance (ANCHSS) surveys among pregnant women attending ANC services, which have become an important component of HIV surveillance in the country.
The main aim of the annual–biennial surveys was to estimate HIV prevalence by age and location (province and district) over time and to generate input data for models used to produce national HIV prevalence and incidence estimates for planning and resource allocation. These models include Spectrum, Thembisa, and Naomi.
Over time, the objectives, inclusion criteria, sampling procedures, and data collection methods have evolved in response to changes in surveillance needs and global HIV monitoring guidelines.
This report reviews the objectives of past ANCHSS surveys and methodological changes over time, and discusses opportunities for using routine ANC and vertical transmission prevention data for HIV surveillance among pregnant women.
Results of past ANC surveys
At the national level, HIV prevalence measured in the survey increased rapidly from 0.8% in 1990 to 22.8% in 1998. Prevalence then rose more slowly, reaching 30.2% in 2005, and remained around 30% until 2022, when it declined to 27.5%.
Syphilis seroprevalence decreased steadily from 11% in 1997 to 1.6% in 2004. It then fluctuated between 1.8% and 2.9% from 2005 to 2007, before stabilising between 1.5% and 1.8% from 2008 to 2011. Measurement of syphilis seroprevalence was paused until 2015, when it was recorded at 2.0%. Since then, seroprevalence has increased, reaching 2.6% in 2019 and 3.1% in 2022.
Future directions
Since the late 1990s, concerns have been raised about ANCHSS, including unlinked anonymous HIV testing, duplicate testing, lack of consent, survey costs, and limited integration with routine ANC and vertical transmission prevention (VTP) data systems. With near-universal HIV testing and increasing ANC coverage, there have been calls since 2013 to transition to HIV surveillance using routine ANC and VTP data, provided quality is sufficient. The 2017 assessments showed high agreement between survey and routine HIV results, but data completeness, quality assurance, and standardisation were sub-optimal. Further assessments and improvements are needed before a national transition can occur, while sentinel surveys remain useful for capturing indicators not available through routine data.
For a more in-depth look into this thought-provoking series download the full PDF below
