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Scientists have focused on a handful of mutations in the coronavirus that they believe could pose new public health concerns if they circulate widely.
Their goal: the tiny spike proteins that coat the outside of the virus.
It is these proteins that researchers have successfully targeted to create vaccines, using them to prime the body’s immune system to make antibodies to fight the virus. But it was also there that they observed certain mutations that forced vaccine manufacturers to react. A variant first found in South Africa is of particular interest due to mutations in the virus spike protein that can make antibodies less effective against it.
And while none of these changes appear to have resulted in a virus capable of escaping current vaccines, it is an area of intense interest for coronavirus researchers.
“The spike protein is like the key that unlocks our cells,” said Simon Clarke, associate professor of cell microbiology at the University of Reading in the UK. “If you have mutations on the spike protein, it could make that key more efficient, or it could change the structure of the key slightly so that it can still access our cells and the antibodies cannot go there. bind. and prevents it from working.
An initial analysis from Moderna found that while its vaccine appeared to be less effective against the South African variant, the antibodies remained above protection levels. The Pfizer-BioNTech vaccine is only slightly less effective against the South African strain, according to a study that has not yet been peer reviewed.
The coronavirus has likely undergone thousands of changes since it first spread to humans. Several different variants, including one that was first reported in the UK and another that is believed to have emerged in Brazil, are already being followed around the world.
But scientists remain worried about the emergence of other variants of the coronavirus, especially if one emerges that makes vaccines obsolete.
“Mutations can make a virus more transmissible or make a virus less sensitive to certain antibodies, so it’s always a big concern,” Clarke said.
So far, vaccines appear to protect against known variants, said Dr Bruce Y. Lee, professor of health policy and management at the City University of New York. He added that even though a vaccine is less protective against a strain, there are likely benefits, such as preventing more severe cases of Covid-19, which not only helps patients but also minimizes pressure on hospitals. and health workers.
“It’s like even though a flu shot is 30% effective, we still recommend getting the flu shot,” Lee said.
But that doesn’t mean there aren’t risks just yet – especially with the critical role the virus spike protein plays.
The South African variant and the British variant contain a spike protein mutation called N501Y which is believed to make these strains more contagious. The South African variant also carries a mutation known as E484K, also on the spike protein, which could make it less sensitive to antibodies produced by vaccines or to those from natural infection.
And because the vaccines target the spike protein, Lee said, there are concerns that mutations in this part of the virus could affect how well the vaccines work.
“If you modify the spike protein enough, the question becomes: how will the immune response change?” he said. “The effectiveness of vaccines really depends on our immune response to this spike protein.”
Research is still ongoing, but observed declines in vaccine efficacy have already prompted Moderna to start tweaking its existing vaccine to make it more effective against emerging strains. Although Moderna’s vaccine appears to be protective against known variants, company CEO Stéphane Bancel said last month that upgrades are being developed “out of caution.”
AstraZeneca and the University of Oxford, which have jointly developed a vaccine approved for use in the UK but not yet in the US, on Wednesday announced plans to produce an improved version to protect against known variants. which may be available in the fall.
And scientists expect more variants to emerge as the pandemic evolves. British scientists reported on Tuesday that the E484K mutation seen in the South African variant has also been found in a small number of cases involving the British strain in England.
“The more a virus replicates, the more likely you are to experience random changes,” Lee said. “A lot of these changes won’t make any difference, but every once in a while you will get a change that will give the virus an edge – making the virus more apt to survive, to replicate, or to infect people.”
This prospect adds to the urgency for countries around the world to aggressively control the spread of the virus, thereby limiting the possibility of the circulation of new, more problematic variants.
“What we do can really affect the trajectory of the pandemic in the weeks to come,” Lee said.
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