The coronavirus strain that conquered South Africa with its incredible ability to infect people who had previously contracted COVID-19 is now in California and at least three other states. More than any other version of the virus, it has proven to be able to escape vaccines designed to block it.
Is another wave fueled by the South African strain inevitable here?
Difficultly. The evolving coronavirus can have many tricks up its sleeve, but scientists say they do too.
Growing evidence that several vaccines are less effective in neutralizing the South African strain is “disturbing news”, but “not all is lost,” said Dr. Anthony Fauci, the country’s leading infectious disease specialist. Vaccination “still suppresses the virus,” he said.
And while the emergence of new variants capable of “escaping” some of the immune system’s antibodies is a cause for concern, the infinite twisting of hands “is a narrative that we have to correct,” said Larry Luchsinger, scientist at the New York Blood Center .
In fact, after almost a year of anguish and worry, the pandemic’s latest challenge has brought out an unusual positive side in many scientists. Yes, some water was spilled, they say. But they are quick to point out that this glass is still more than half full.
Why? Because the numbers are important, 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, said Luchsinger.
Concerns were raised by clinical trials involving several COVID-19 vaccines.
For example, a Johnson & Johnson vaccine that reduced the risk of moderate to severe cases of COVID-19 in the U.S. by 72% was only 57% effective in reducing that risk in South Africa, where the coronavirus strain known as B. 1,351 dominates. Likewise, a Novavax vaccine that reduced the risk of all types of COVID-19 by almost 90% in Britain was only 49% effective in South Africa.
The difference can also be seen by comparing clinical trials at different times. When the COVID-19 vaccine developed by AstraZeneca and the University of Oxford was tested in South Africa several months ago, those who received it were 75% less likely to develop mild to moderate disease than their counterparts who received a placebo. However, after B.1.351 took control, the AstraZeneca vaccine offered no advantage over placebo.
The tests carried out in the laboratory were also worrisome. For example, antibodies generated by people who received the Pfizer-BioNTech vaccine were not as adept at blocking a modified version of the South African virus as they were at preventing modified versions of another UK strain, according to results published this week. in the journal Nature Medicine.
To understand why these seemingly worrying developments are not causing panic in scientists, it is useful to know that the process by which antibodies neutralize floating viral particles is a chaotic, inefficient and repetitive game of success and failure.
Whether induced by vaccination or natural infection, antibodies routinely attach to their viral invaders, fall off and cause new ones to take their place. This inefficiency requires the immune system to build legions of neutralizing antibodies that are diverse and abundant enough to dominate more viral targets than any infection could present, Luchsinger said.
Even when a virus acquires a mutation that makes antibodies less able to neutralize 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 one from Moderna against several of the new variants of the coronavirus.
The researchers extracted antibodies from 20 vaccinated volunteers. In laboratory dishes, these antibodies were able to “potently neutralize” all variants of the coronavirus that the researchers threw at them, according to a study published this week in the journal Nature.
This sunny image was obscured – but not eclipsed – by a worrying discovery: if you looked only at the 17 most powerful 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 trademarks of the South African strain.
This may sound alarming, but it actually shows the power of the immune system’s response to these specific vaccines. If the antibodies and other immune proteins generated by the vaccination were a team, their bench would be so deep that 14 of their top 17 players could be injured or sent to the locker room and still prevail over South Africa’s viral variant.
Even though viruses escape some antibodies, the adaptive immune system lives up to its name. After learning to recognize the original Wuhan virus, whether through a vaccine or a previous infection, an encounter with the South African strain causes the body’s white blood cells to produce antibodies that improve on the target of the altered virus.
“He adapts,” said Luchsinger.
In fact, this probably explains why vaccines that show reduced efficacy 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. At the most recent trial there, none of the participants developed serious illness, so the jury has yet to decide.
“This vaccine can still protect against at least severe COVID-19, especially in individuals at high risk of developing serious illness,” said Dr. Shabir Madhi, a vaccine specialist at the University of Witwatersrand in Johannesburg. That may be as much as can be expected from a vaccine, he added.
Scientists are also encouraged that the South African strain does not appear to be more transmissible than its predecessors. Although it reached the coast of the United States, it is not likely to spread aggressively. This will give us more time to step up vaccinations and deny B.1.351 the chance to gain a solid foothold here, said Fauci.
Dr. Stanley Perlman, a microbiologist at the University of Iowa who has studied coronavirus for decades, said he is confused by the genetic changes that have made the South African strain better at avoiding antibodies, but apparently not more transmissible. Overall, he said, the best strategy for a virus to sustain an outbreak and continue to find new hosts is to change it in a way that allows it to spread more quickly.
Perlman suspects that one of the B.1.351 mutations does something sneaky – like improving the virus’s ability to enter cells – that has yet to be discovered. There may still be surprises at the store, he said.
But there is a backup plan for that too. As researchers analyze the mutations they see emerging, they learn more about what each change does, who the problem creators are and how they can work together.
Insights like these will help them to reshape vaccines to improve their effectiveness and create boosters for people who have already been immunized.
“It is not a hindrance if the virus continues to evolve, which I hope will,” said Dr. Bruce Walker, founding director of the Ragon Institute in Boston, which is dedicated to the study of the immune system. “We deal with the flu every year,” reformulating the vaccine. “We can do this here.”
Scientists are also discovering the virus’s secrets. Recurrent patterns of mutations from different parts of the world have given them clues as to which strategies increase the virus’s fitness. This, in turn, suggests which viral structures are most likely to change and how.
“The virus is telling us what is comfortable,” said Walker, and this knowledge can help scientists anticipate their next moves.