South African antibodies study sheds more light on Covid-19 infections
“We expect these results to withstand significant scrutiny
PROFESSOR ALEX WELTE SACEMA
THE Covid-19 infections might exceed officially diagnosed cases by a factor of 10, suggests an SA National Blood Service (SANBS) and Western Cape Blood Service (WCBS) study of Sars-CoV-2 antibodies among blood donors in four provinces.
Released on Wednesday, the survey, known as a seroprevalence study of healthy consenting blood donors, aims to determine how many donors have Sars-CoV-2 antibodies, which would be an indication of previous infection with the virus that causes Covid-19.
Donors can donate blood after they have recovered from the illness and have been free of symptoms for at least 14 days.
When weighted against the general population, an estimated seroprevalence of 63% in the Eastern Cape, 32% in the Northern Cape, 46% in the Free State and 52% in KwaZulu-Natal was found. There was no significant difference in seroprevalence by sex or age groups, however, race was a highly statistically significant factor.
There is no biological reason for race itself being a factor in contracting Sars-CoV-2, and this finding needed further investigation, the SANBS said.
“We agreed to publish these numbers so that the discussions about lockdown levels, vaccine distribution, (and) the circulation of novel variants can take place with all available information in play,” said principal investigator and SANBS acting chief operations officer Marion Vermeulen.
“Expansion of the testing to other provinces is being planned and will be concluded upon regulatory approval of the testing reagents available for the high throughput platform.
“The current analysis we have paints a picture with some consistent features across four provinces, so we believe these results are suggestive of what we would find in the other five provinces,” Vermeulen added.
Professor Alex Welte, of the SA Centre for Epidemiological Modelling and Analysis (SACEMA), an analytical consultant to the project, mentioned study limitations, including that blood donors were HIV negative.
“From previous work, we know that blood donors are pretty representative of the general public. We expect these results to withstand significant scrutiny, and I hope resources are available for the blood services to continue this work, which is probably the most cost-effective way to monitor the overall scale of Covid infection in the country.”
Dr Karin van den Berg, lead consultant in translational research at SANBS, said other countries had seen large outbreaks even after such strikingly high seroprevalence was reported. “The emergence of variant strains likely contributes to this phenomenon,” she said.