South African Coronavirus Variant May Dodge Existing Immunity in Some People

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A woman at the Baragwanath hospital in Soweto, South Africa receiving an injection as a part of a covid-19 vaccine trial in June 2020.
A woman at the Baragwanath hospital in Soweto, South Africa receiving an injection as a part of a covid-19 vaccine trial in June 2020.
Photo: Siphiwe Sibeko/AFP (Getty Images)

Experts are becoming increasingly worried that at least some variants of the coronavirus will pose an added challenge to limiting the spread of covid-19 through vaccination. Recent data announced over the weekend suggests a variant first found in South Africa can escape detection from antibodies in some people who had been infected with older versions of the virus. Though it’s very unlikely these variants will completely evade vaccine-provided immunity, scientists are preparing for the possibility that vaccines will have to be adjusted to better match newer strains circulating in the population.

In mid-December, scientists in both the UK and South Africa announced the emergence of new strains of the coronavirus that contained worrying genetic variations. Though the variants shared some mutations, they’re believed to have evolved independently. Both the UK variant—known as 20I/501Y.V1 or B.1.1.7—and the South African variant—called 20H/501Y.V2 or B.1.351—were quickly determined to be more transmissible than previously common strains in those communities.


Viruses mutate all the time, but what’s made B.1.1.7, B.1.351, and other similar variants so worrying to scientists is their collection of multiple mutations connected to the spike protein, a key part of the virus that helps it break into cells to make more of itself. Enough mutations in the right places can change the relationship between a virus and its host, including its ability to infect people whose immune system has already been trained to recognize the virus, either through natural infection or vaccination. And that’s a concern that’s starting to look more real for B.1.351 in particular.

On Monday, The National Institute for Communicable Diseases (NICD)—South Africa’s public health agency—announced the results of early work studying B.1.351 and immunity. They exposed the variant to blood samples from 44 covid-19 survivors, looking to see whether the virus would survive against neutralizing antibodies created to an earlier infection.

“The blood samples from half the people we tested showed that all neutralizing activity was lost,” the NICD wrote on its website. “This suggests that they may no longer be protected from re-infection.”

In more than 90% of the samples, there was also at least some reduction in the neutralizing ability displayed by antibodies. That’s a harder finding to evaluate, but it could suggest that some reduced immunity should be expected in people infected early in the pandemic who are then exposed to B.1.351.


These findings are still preliminary and based on a small sample size. And as we’ve said numerous times, immunity is complicated. Antibodies are a crucial aspect of our immune system, but they’re not the only part. Our T cells and B cells are also key, and it would take a lot for any variant to bypass all of these defenses at once. This might mean that B.1.351 and similar variants can cause reinfections, but those reinfections might on average be milder than the first time. For people already vaccinated against the coronavirus, this data suggests that B.1.351 might be able to cause sickness more often than earlier variants could. But again, it would likely cause less illness (and less severe illness) on average in vaccinated people than in those with no protection at all. Not all variants are the same, and the effects they have on immunity and transmission will depend heavily on how widespread a variant becomes in the community.


All that said, the new data from South Africa is indeed troubling. The UK and South African variants are already spreading in several countries, and experts fear they will soon become prevalent in these places. Over the weekend, scientists with the Centers for Disease Control and Prevention released a paper predicting that the B.1.1.7 variant would likely become the dominant strain in the U.S. by March.

Right now, the same CDC model predicts that higher levels of vaccination over time will greatly reduce the transmission of any variants, including B.1.1.7—an opinion widely held by many outside scientists as well. Even a vaccine that loses some effectiveness due to these variants will probably still have a potent impact on reducing illness and transmission, much as vaccines for quickly mutating viral diseases like the flu do.


But these new findings, which are expected to be presented in full by the South African government in a few weeks, do indicate that we have to keep a close eye on the virus as it continues to evolve. Moderna and Pfizer/BioNTech—the companies behind the first two vaccines to reach the American public—have stated that their vaccines should be effective against the variants found so far, but they have also said that their vaccines can be modified to better match the newer strains if needed. Data from studying other human coronaviruses has also suggested that covid-19 vaccines will need to be periodically updated to keep up with the changing virus.

More than anything, these developments should highlight why it’s more important than ever to lower our risk of catching and transmitting covid-19. No matter how many mutations the coronavirus picks up, it hasn’t stopped being reliant on humans to keep spreading. Wearing masks and avoiding close, prolonged contact indoors with large groups of people altogether will still help bring a faster end to the pandemic.