‘Most South Africans have had COVID-19' — National Blood Service study

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More than half of South Africans probably have already been infected with SARS-CoV-2, with blacks three-to-five times more likely than white people to have antibodies to the virus, found a SA National Blood Service study.

Despite this, "As has been seen in other areas, even such high seroprevalence does not guarantee population-level immunity against new outbreaks – probably due to viral evolution and waning of antibody neutralisation," reports the study, which extrapolates  to the entire population an analysis of blood donors.

In a Business Insider report, Discovery Group CEO and founder Adrian Gore agrees with the SANBS conclusion, saying that South Africa’s sky-high "excess" death number indicates that more than 50% of population had already been infected with COVID-19.

Based on the excess death rate, Discovery estimates the country’s true infection rate must be above half of the population. “The number of people who have been infected in our view is probably over 50% of the country. This pandemic has had a traumatic effect on people, on the economy. You have to fight it with everything you can,” Gore said.

Groundup reports that the study led by authors from the National Blood Service, shows that a large percentage of the population has likely already been infected with SARS-CoV-2 and that there are striking differences in prevalence between blacks and whites.

Over seven days between 7 and 25 January, 4,858 blood donors were tested for antibodies to the virus that causes COVID-19. These antibodies help the body neutralise the effects of SARS-CoV-2 and we have them only if we have been previously infected.

The tests were done in four provinces: 1,457 in Eastern Cape; 463 in Northern Cape; 831 in Free State and 2,107 in KwaZulu-Natal.

Extrapolating their results to the whole population, the researchers estimated that 63% of people in Eastern Cape have been infected since the epidemic started, 32% in Northern Cape, 46% in Free State and 52% in KwaZulu-Natal. This is massively more than the clinically confirmed case rates of between 2 and 3% in these four provinces.

Particularly striking was the difference between races. Black people were between three (Northern Cape) and five (KwaZulu-Natal) times more likely than white people to have antibodies to the virus. Asians in KwaZulu-Natal had higher prevalence than whites, but lower than blacks. The researchers did not find any significant differences across age or sex.

“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 researchers write.

The authors acknowledge that blood donors are not representative of the South African population but write: “It seems plausible that these estimates are reasonably generalisable to actual population level anti-SARS-CoV-2 seroprevalence, but should be further verified.”

The study has not yet been peer-reviewed.

What about the new variant?
The extent to which antibodies against the original form of the coronavirus offer protection against the new variant 501Y.V2, first detected in South Africa in November, is unknown. But it seems likely given that the study was undertaken last month that a significant proportion of donors were at some point infected with 501Y.V2.

Are we reaching herd immunity?
The herd immunity threshold changes from area to area and time to time depending on whether people are physically distancing, wearing masks, and reducing the number of large events they attend.

But perhaps the key question is this: are we approaching the herd immunity threshold so that we can return to the way we lived before lockdown? It’s hard to be sure but probably not yet. There is still room for a third wave (especially in predominantly white suburbs).

Also, we still don’t know enough about how likely people are to become re-infected with the 501Y.V2 strain or future strains that may evolve. We also don’t know how much less likely people are to become very ill the second time they are infected.

How does this compare with other prevalence studies?
Last year, long before the second wave, 35 to 41% seroprevalence was found among pregnant women and people with HIV attending public clinics in Cape Town. In Nairobi, Kenya in November, a survey found 35% of residents had SARS-CoV-2 antibodies. A recent study in Delhi, India found more than half the population had been infected.

But surveys in Europe and North America have usually reported much lower prevalence.

This explains the high Eastern Cape excess death rate
The Medical Research Council, this past week, reported excess deaths per province since the epidemic began. The Eastern Cape’s excess death rate is extraordinarily high: 485 per 100,000 people. This is far higher than the official COVID-19 infection mortality rate for any country in the world. But with the blood bank survey finding the infection mortality rate in the Eastern Cape can be estimated. It’s about 0.8%, which is in the range of plausible death rates for SARS-CoV-2.

Why is race still used?
It would be a “head-in-the-sand” approach to pretend there are no socio-economic differences in South Africa between races as defined under apartheid. Race is still a predictor of health for most of the country. It was important for the researchers to study this.

 

Study details
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.

Wendy Sykes, Laurette Mhlanga, Ronel Swanevelder, Tanya Nadia Glatt, Eduard Grebe, Charl Coleman, Nadia Pieterson, Russell Cable, Alex Welte, Karin van den Berg, Marion Vermeulen

Study yet to be peer reviewed

Abstract
Background
Population-level estimates of prevalence of anti-SARS-CoV-2 antibody positivity (seroprevalence) is a crucial epidemiological indicator for tracking the Covid-19 epidemic. Such data are in short supply, both internationally and in South Africa. The South African blood services (the South African National Blood Service, SANBS and the Western Cape Blood Service, WCBS) are coordinating a nationally representative survey of blood donors, which it is hoped can become a cost-effective surveillance method with validity for community-level seroprevalence estimation.
Methods
Leveraging existing arrangements, SANBS human research ethics committee permission was obtained to test blood donations collected on predefined days (7th, 10th ,12th ,15th ,20th ,23th and 25th January) for anti-SARS-CoV-2 antibodies, using the Roche Elecsys Anti-SARS-CoV-2 assay on the cobas e411 platform currently available in the blood services’ donation testing laboratories. Using standard methods, prevalence analysis was done by province, age and race, allowing age to be regarded as either a continuous or categorical variable. Testing was performed in the Eastern Cape (EC), Free State (FS), KwaZulu Natal (ZN) and Northern Cape (NC) provinces.
Results
We report on data from 4858 donors – 1457 in EC; 463 in NC; 831 in FS and 2107 in ZN. Prevalence varied substantially across race groups and between provinces, with seroprevalence among Black donors consistently several times higher than among White donors, and the other main population groups (Coloured and Asian) not consistently represented in all provinces. There is no clear evidence that seroprevalence among donors varies by age. Weighted net estimates of prevalence (in the core age range 15-69) by province (compared with official clinically-confirmed COVID-19 case rates in mid-January 2021) are: EC-63%(2.8%), NC-32%(2.2%), FS-46%(2.4%), and ZN-52%(2.4%).
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. As has been seen in other areas, even such high seroprevalence does not guarantee population-level immunity against new outbreaks – probably due to viral evolution and waning of antibody neutralization. Despite its limitations, notably a ‘healthy donor’ effect, it seems plausible that these estimates are reasonably generalisable to actual population level anti-SARS-CoV-2 seroprevalence, but should be further verified.

 

However, a Cape Times report notes that the results have been questioned by health experts in the Eastern Cape who feel not enough testing was done and the samples collected were not random.

 

Discovery Group CEO and founder Adrian Gore agrees that South Africa’s sky-high "excess" death number indicates that more than 50% of South Africa’s population have already been infected with COVID-19. According to a Business Insider report, Gore said in an interview that there’s “absolutely no ambiguity” that the excess deaths are linked to COVID-19.

Based on the excess death rate, Discovery estimates the country’s true infection rate must be above half of the population. “The number of people who have been infected in our view is probably over 50% of the country. This pandemic has had a traumatic effect on people, on the economy. You have to fight it with everything you can,” Gore said.

Commenting on the SANBS survey, Gore said that the high infection rate could provide some protection against the feared third wave of the pandemic, which could hit South Africa in the coming, colder months. “We are hoping that a third wave may take longer and might be less because we think the infection rate has been high.

And, the report says, while government’s handling of vaccine procurement has come under fire, Gore supported its centralised approach in distributing vaccines, which prohibits private companies from procuring vaccines. “Not following this process would mean low-risk people get vaccinated before the clinically vulnerable, resulting in unnecessary illness and death. This cannot and should not happen,” Gore said.

He said in his LinkedIn post that Discovery has not agreed to subsidise vaccines for non-members. “This is simply not true.” While government still has to set a price for vaccines, Gore believes this should not be an issue, given the benefits of rolling out the vaccines as quickly as possible to members.

 

Full Groundup report (Open access)

 

Study (yet to be peer reviewed)

 

Full Cape Times report (Open access)

 

Full Business Insider report (Open access)

 

LinkedIn post

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