Relatively low levels of coronavirus antibodies among adults in Gauteng compared with other provinces may partly explain why infections have spread so fast in the region, researchers say.
Gauteng is bearing the brunt of SA’s surge in coronavirus infections, accounting for more than 65% of the 15,036 new cases registered in SA on June 27.
Analysis of samples provided by blood donors reveal the prevalence of antibodies to SARS-Cov-2, the virus that causes Covid-19, ranged from 35.1% in Gauteng to 62.5% in the Eastern Cape.
The research was conducted by the SA National Blood Service (SANBS), the Western Cape Blood Service, and the SA Centre for Epidemiological Modelling and Analysis (Sacema) at Stellenbosch University, and has not yet been peer-reviewed.
While relatively low antibody levels in Gauteng, which suggests a relatively larger proportion of its population is vulnerable to infection, may partly explain its sharp rise in cases, other factors such as the recent detection of the Delta variant could also play a role, said Alex Welte, research professor at Sacema.
The variant, which was first detected in India in October 2020, is more transmissible than the original strain of coronavirus first detected in Wuhan. It has rapidly spread around the world and has now been identified in at least 85 countries.
It has displaced the Beta variant in KwaZulu-Natal, and has been detected with increasing prevalence in the Western Cape, but there is limited data for Gauteng, according to research presented to the media at the weekend by scientists from the KwaZulu-Natal Research and Innovation Sequencing Platform at the University of KwaZulu-Natal.
The study was conducted in two stages, with samples collected from the Eastern Cape, the Northern Cape, Free State and KwaZulu-Natal in January, as these provinces emerged from the second wave. The remaining five provinces were sampled in May, once the test kits used in these provinces had been approved by the SA Health Products Regulatory Authority. This was before SA’s third wave got under way.
Antibodies were detected using the Roche Elecsys platform, which the researchers said was designed to detect antibodies generated in response to the nucleocapsid proteins of the virus. These antibodies are only made in response to natural infection and remain detectable in most people for at least a year, they said. The tests could not detect antibodies generated in response to vaccines, which target the spike protein of the virus.
Antibodies are proteins produced by the body’s immune system in response to infections, and help eliminate disease-causing pathogens. The study estimated that 43% of SA’s population of SA has antibodies to SARS-CoV-2.
SANBS director Karin van den Berg said interviews with a subset of donors indicated a small proportion of people who had been formally diagnosed with Covid-19 did not have detectable antibodies, while a “large majority” who had detectable antibodies had never received a formal diagnosis of Covid-19.
Welte said the researchers intend to submit the study to the peer-review journal PLOS One.
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