SIB#441- Herd Immunity- Are we getting closer?

The Study: Prevalence of anti-SARS-CoV-2 antibodies among blood donors in Northern Cape, KwaZulu-Natal, Easter Cape, and Free State provinces of South Africa in January 2021

 

Overview: This is a prepublication study (still in peer review) which provides some population level estimates of the presence of SARS-Cov-2 antibodies based on seroprevalence evidence from a large sample of blood donors across four separate provinces of South Africa.

 

Key Points: 

  • ·        The study looked at data from 4858 blood donors across four South African provinces. 

  • ·        The core age range of the blood donors was 15-69 years. 

  • ·        Prevalence of SARS-CoV-2 antibodies varied substantially across race groups and between the four different provinces. 

  • ·        Seroprevalence among Black donors was “several times higher than among White donors as well as other demographic groups. 

  • ·        There was no evidence that seroprevalence of antibodies varied according to age. 

  • ·        Weighted net estimates of antibody prevalence ranged from a low of 32% (Northern Cape) to a high of 63% (Eastern Cape).  Donors from the remaining two provinces, Free State and KwaZulu-Natal, demonstrated seroprevalence rates of 46% and 52% respectively.   

     

    Author’s Conclusions: “Our study demonstrates substantial differences in dissemination of SARS-CoV-2 infection between different race groups, most likely explained by historically based differences in socio-economic status and housing conditions.” The authors conclude that these estimates are “reasonably generalisable to actual population level anti-SARS-CoV-2 seroprevalence but should be further verified.” They also stress that “even such high seroprevalence does not guarantee population-level immunity.”

 Reviewer's Comments: The higher ranges of seroprevalence seen in the Eastern Cape province (63%) are the first I have seen which seem to be getting close to where it is hypothesized that herd immunity starts making it more difficult for the virus to find a path to uninfected population.  Most sources theorize that herd immunity will probably begin somewhere around 70(ish) percent but obviously that will be impacted by a wide range of socio economic and other factors unique to every community.

 I have chosen to include this information because in my view it provides timely and encouraging evidence of continued progress toward natural herd immunity as the virus makes its way through various populations. Nothing here should be taken as advice against vaccination or that the attendant dangers of the viral pandemic have passed. High risk individuals should continue to protect themselves.

  

Reviewer:  Mark R. Payne DC 

Reference: Wendy Sykes 1 , Laurette Mhlanga 2 , Ronel Swanevelder 1 , Tanya Nadia Glatt 1 , Eduard Grebe 2,4,5 , Charl Coleman 1 , Nadia Pieterson 3 , Russel Cable 3 , Alex Welte 2 , Karin van den Berg 1,6,7 , Marion Vermeulen 1,7. Prevalence of anti-SARS-CoV-2 antibodies among blood donors in Northern Cape, KwaZulu-Natal, Eastern Cape, and Free State provinces of South Africa in January 2021. Prepublication- Research Square

 Link to Full Text: https://assets.researchsquare.com/files/rs-233375/v1_stamped.pdf

 

 

Mark R. Payne DC