The coronavirus strain that took South Africa by storm with its uncanny ability to infect people who were already sick with COVID-19 is now in California and at least three other states. More than any other version of the virus, it has proven its ability to evade the vaccines designed to block it.
Is another wave sparked by South African tension inevitable here?
Barely. The evolving coronavirus may have plenty of tricks up its sleeve, but scientists say they do.
The growing evidence that different vaccines are less efficient at neutralizing the South African strain is “troubling news,” but “all is not lost,” said Dr. Anthony Fauci, the world’s leading infectious disease expert. Vaccination “still suppresses the virus,” he said.
And while the emergence of new variants that can ‘escape’ some of the immune system’s antibodies is a cause for concern, the endless handwringing is ‘a story we need to correct,’ said Larry Luchsinger, a scientist at the New York Blood Center.
Indeed, after nearly a year of woe and worry, the pandemic’s latest challenge has brought out an unusually bright side in many scientists. Yes, some water has been spilled, they say. But they are quick to point out that this glass is still much more than half full.
Why? Because numbers matter, and even an elusive target like the South African variant is unlikely to completely escape the overwhelming number of antibodies generated by current vaccines or a previous infection, Luchsinger said.
Concerns were raised by clinical trials with multiple COVID-19 vaccines.
For example, a Johnson & Johnson vaccine that reduced the risk of moderate to severe cases of COVID-19 in the US by 72% was only 57% effective in reducing that risk in South Africa, where the coronavirus strain is known as B .1.351. dominates. Likewise, a Novavax vaccine that reduced the risk of all types of COVID-19 in Great Britain by nearly 90% was only 49% effective in South Africa.
The difference could also be seen by comparing clinical studies at different time points. When the COVID-19 vaccine, developed by AstraZeneca and Oxford University, was tested in South Africa several months ago, those who received it were 75% less likely to develop mild to moderate illnesses than their counterparts who received a placebo. But after B.1.351 took over, the AstraZeneca vaccine offered no benefit over placebo.
Tests conducted in laboratory settings were also of concern. For example, antibodies generated by people who received the Pfizer-BioNTech vaccine were not as adept at blocking an engineered version of the virus from South Africa as they were at stopping engineered versions of another strain from the United Kingdom , according to published results. this week in the journal Nature Medicine.
To understand why scientists don’t panic about these seemingly troubling developments, it helps to know that the process by which antibodies neutralize free-floating viral particles is a chaotic, inefficient and repetitive hit-and-miss game.
Whether induced by vaccination or natural infection, antibodies routinely cling to their viral invaders, falling off and swiping new ones in to take their place. That inefficiency requires the immune system to build legions of neutralizing antibodies that are diverse and abundant enough to overwhelm more viral targets than most infections can present, Luchsinger said.
Even when a virus acquires a mutation that makes antibodies less adept at neutralizing its targets, there is still so much redundancy that the virus remains vulnerable, he said.
Scientists at Caltech and Rockefeller University saw this in action when they put antibodies induced by the Pfizer-BioNTech vaccine and a similar vaccine from Moderna against several of the new coronavirus variants.
The researchers obtained antibodies from 20 vaccinated volunteers. In lab dishes, those antibodies were able to “ powerfully neutralize ” any coronavirus variant the researchers threw at them, according to a study published this week in the journal Nature.
That sunny picture was clouded – but not overshadowed – by a worrying finding: Looking only at the 17 most potent antibodies produced in response to the two vaccines, in 14 cases the neutralizing effect was ‘reduced or abolished’ by the presence of a mutation called E484K, one of the hallmarks of the South African strain.
That may sound alarming, but it actually testifies to the strength of the immune system’s response to these particular vaccines. If the antibodies and other immune proteins generated by vaccination were a team, the couch would be so deep that 14 of the top 17 players could be injured or sent to the locker room and it would still triumph over the viral variety of South Africa.
Even when viruses evade certain antibodies, the adaptive immune system lives up to its name. After learning to recognize the original Wuhan virus, either through a vaccine or a previous infection, an encounter with the South African tribe prompts the body’s white blood cells to produce antibodies that can better target the altered virus.
“It’s adapting,” said Luchsinger.
That probably explains why vaccines that show reduced effectiveness against the South African variant still work well enough to prevent serious illness, hospitalization and death from COVID-19.
In South Africa, researchers remain hopeful that the AstraZeneca vaccine will follow this pattern. In the most recent trial there, none of the participants developed any serious illness, so the jury is out yet.
“This vaccine may still protect against severe COVID-19, especially in individuals who are at high risk of developing serious disease,” said Dr. Shabir Madhi, a vaccine expert at the University of the Witwatersrand in Johannesburg. That’s perhaps the most you can expect from a vaccine, he added.
Scientists are also encouraged that the South African species does not appear to be any more transferable than its predecessors. Although it has come to the US shores, it is unlikely to spread aggressively. That will give us more time to ramp up vaccinations and deny B.1.351 the chance to get a solid foothold here, Fauci said.
Dr. Stanley Perlman, a microbiologist at the University of Iowa who has studied coronaviruses for decades, said he is frustrated with genetic changes that have made the South African tribe better at dodging antibodies, but apparently are no longer transmissible. In general, he said, the best strategy for a virus to perpetuate an outbreak and continue to find new hosts is to change ways that make it easier for it to spread.
Perlman suspects that one of the B.1.351 mutations is doing something covert – like improving the virus’ ability to enter cells – that hasn’t worked out yet. There may still be surprises in store, he said.
But there is also a backup plan for that. As researchers sift through the mutations they see coming, they learn more about what each change does, what troublemakers are and how they can work together.
Such insights will help them reformulate vaccines to improve their effectiveness and create boosters for people who have already been immunized.
“It’s not a showstopper if the virus continues to develop, which is what I expect,” said Dr. Bruce Walker, the founder and director of the Ragon Institute in Boston, which is dedicated to research into the immune system. “Every year we treat the flu” by reformulating the vaccine. “We can do that here.”
Scientists are also prying open the secrets of the virus. Recurring patterns of mutations arising from different corners of the world have provided clues as to which strategies improve the condition of the virus. That, in turn, suggests which viral structures are most likely to change, and how.
“The virus tells us what it’s comfortable with,” Walker said, and that knowledge could help scientists anticipate next steps.