Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) was identified in December 2019. It causes the illness known as coronavirus disease 2019 (COVID-19) and has to date resulted in over 2.8 million cases and 85 000 deaths in South Africa (www.sacoronavirus.co.za).
Seroprevalence or seroepidemiological surveys are a useful tool to track the transmission of infection in different population groups. WCBS embarked on a seroprevalence survey to quantify the proportion of our staff who have antibodies against SARS-CoV-2, as well as provide information on those who have not produced antibodies and remain susceptible to the virus.
This study focused on all staff at WCBS who volunteered to donate samples to be screened for SARS-CoV-2 antibodies. There were no exclusion criteria for participants. The study commenced in November 2020, after the first wave hit South Africa. Samples were tested using the Roche Elecsys anti-SARS-CoV-2 total immunoglobulin nucleocapsid assay on the Cobas e801 platform in use at WCBS.
Results showed an overall SARS-CoV-2 seroprevalence of 24%. Of that percentage, 46% of individuals were asymptomatic. Figure 1 shows the division by site – our Paarl and Worcester regional branches, and blood banks in the Cape Metropole and Somerset West, had the highest prevalence compared to other staff groups. This could be attributed to front-line clinic staff being exposed to the public more than other groups that are confined to offices. Our George regional branch surprisingly had the lowest prevalence, despite the town being categorised as an epicentre in the Western Cape during the first wave.
There was no clinical significance between age, gender and race in the study participants. We tested the blood group of individuals to determine if a putative protective relationship exists between blood groups and COVID-19 severity, but could not find any significance (figure 2). This survey provided essential data for WCBS and was used to assess our risk management strategies to reduce viral transmission.
Figure 1: Anti-SARS-CoV-2 prevalence percentage per WCBS site
Figure 2: Seroprevalence percentage per blood group
For more information, please contact Nadia Pietersen, Manager – Transfusion Virology (Nadiap@wcbs.org.za)