Of the blood samples taken from people who had already recovered from COVID-19, 48% showed a complete escape from neutralizing antibodies when tested against the South African variant, according to the Global Virus Network. That one figure explains why scientists took Beta so seriously.
Beta goes by several names: 501Y.V2, B.1.351 and 20H. South African researchers first described it in a Nature paper. The lineage turned up after the country’s first wave, in Nelson Mandela Bay, a coastal metro in the Eastern Cape, and detection dates to October 2020. Within weeks it was dominant in the Eastern Cape, Western Cape and KwaZulu-Natal. By January 2021 it made up 97% of cases in South Africa, according to GISAID data cited in a second Nature paper.
What changed in the virus
Here is what that means in plain terms. The coronavirus uses a spike protein to grab hold of our cells. Beta carries eight mutations in the spike. Three of them, K417N, E484K and N501Y, sit in the part that makes direct contact, the receptor-binding domain. Think of it like a key whose teeth have been filed down: it still opens the lock, but antibodies trained to recognize the old shape have a harder time gripping it.
Researchers said the spread pointed to a selection advantage, most plausibly from greater transmissibility or immune escape. South African scientists said this variant was 50% more infectious than earlier ones, Reuters reported on 20 January 2021, and it had reached at least 20 countries after the WHO was told in late December. It drove most of South Africa’s second wave, which peaked above 21,000 daily cases before easing to about 12,000.
Immunity from earlier infection
The Nature team compared plasma from people hospitalized in the first and second waves. Plasma from first-wave patients neutralized the first-wave virus well, but it struggled with Beta: the effect fell 15.1-fold compared with plasma from people infected in the second wave. The other direction worked better. Plasma from second-wave patients showed only a 2.3-fold drop against first-wave virus. That gave some preliminary reason to think vaccines designed from the variant’s sequence could still work against other circulating lineages.
A separate group, drawn from three South African universities and the country’s national communicable diseases institute, posted a preprint with a stark finding: Beta showed “complete escape from three classes of therapeutically relevant monoclonal antibodies.” The same paper warned of “the prospect of reinfection.”
What it meant for vaccines
The practical upshot was lower protection in the field. According to the Global Virus Network, Novavax reported 89% efficacy in the UK but 60% in South Africa. Johnson and Johnson’s single-dose vaccine gave 72% protection against moderate to severe illness in the US, 66% in Latin America and only 57% in South Africa. Its protection against severe disease was better, at 85% after 28 days. For AstraZeneca, the picture was worse: overall efficacy against COVID-19 of any severity was 33.5%, measured over two weeks after the first dose, and trials showed no protection against mild or moderate illness from the variant.
Sources
- Detection of a SARS-CoV-2 variant of concern in South Africa | Nature
- Escape of SARS-CoV-2 501Y.V2 from neutralization by convalescent plasma | Nature
- COVID-19: South African variant defeats plasma treatment – scientists | The Jerusalem Post
- Beta (B.1.351) – Global Virus Network
Sources
- SARS-CoV-2 Beta variant – Wikipedia
- South African Coronavirus Variant May Dodge Existing Immunity in…
