(CNN) Scientists have identified an "escape mutant" that may decrease the efficacy of Covid-19 vaccines.
The mutation -- called E484K -- has been found in a variant of the coronavirus first spotted in South Africa two months ago. That variant has now spread to 12 other countries.
Penny Moore, associate professor at the National Institute for Communicable Diseases in South Africa, called the mutation "alarming."
"We fear this mutation might have an impact, and what we don't know is the extent of the impact," she said.
E484K is called an "escape mutant" because it's been shown it might be able to escape some of the antibodies produced by the vaccine.
"I'm worried," said Alex Sigal, a virologist at the Africa Health Research Institute.
Sigal, Moore, and other scientists who are studying the E484K mutation still have to complete their work in the lab to see if the vaccine is less effective against this new variant.
Based on what they've seen so far, they say they highly doubt E484K will render the coronavirus vaccines useless. Rather, they think there's a possibility the mutation -- on its own or in combination with other mutations -- could decrease the efficacy of the vaccine against the variant.
They also worry E484K might be an indication the novel coronavirus is showing its ability to change before our eyes. If this mutation happened in a matter of months, other problematic mutations could follow.
"This virus may be taking the first steps down a fairly lengthy road towards vaccine resistance," said Andrew Ward, a structural virologist at Scripps Research in La Jolla, California.
"It's the beginning of a long haul," Moore said. "That's what's really shaken me up about this. It's a sobering wake up call."
To understand the potential danger posed by the E484K mutation, picture a teacher in front of a classroom full of rowdy first graders.
After months of trying to get her class under control, the teacher finally nails it. She gets them to sit still in their chairs.
But after a while, one child leaves the class, and another takes his place. This new child -- this new little rascal -- won't sit down. The teacher's technique for calming the children doesn't work with him.
The teacher here is the vaccine, and the rascally student is the E484K mutation.
When the vaccines being used in the US were put to the test this summer and fall, they nailed it, virtually conquering the virus into submission. But since then, parts of the virus have sometimes swapped themselves out for new bits and sometimes those new bits don't behave.
To test out these new bits, researchers at the Fred Hutchinson Cancer Center in Seattle and elsewhere have looked at plasma from patients who recovered from Covid-19 to see if their antibodies can fight off E484K and other mutations.
What they found is that E484K challenges the ability of some antibodies to neutralize the virus.
While the attention has been focused on E484K, scientists are also keeping an eye on other mutations in the variant.
The next step is to test these mutations against antibodies created by vaccines -- that's the work scientists are doing now and hope to announce in the next few weeks.
E484K isn't only in the variant first found in South Africa -- it's recently been found in a variant in Brazil as well.
That variant hasn't been reported in other countries. But according to GISAID, an independent data sharing initiative, the one first spotted in South Africa (its scientific name is 501Y.V2), has now been tracked in 12 other countries: the UK; Botswana; France; Australia; Germany; Switzerland; Japan; Sweden; South Korea; Finland; Ireland and the Netherlands.
But even if E484K -- alone or in combination with other mutations in the variant -- ends up being a problem, the variant likely won't escape all the antibodies produced by vaccines, considering that the vaccines produce many antibodies.
The concern is more for what happens as the virus mutates over and over.
It's not that the coronavirus is such a speedy mutator -- in fact Sigal, one of the South African researchers, called it "a real slowpoke." It's that the virus is spreading so quickly around the world, and each time it goes from person to person, it gets another chance to mutate.
"It creates more opportunities for the virus to learn how to be resistant to the vaccine," said Paul Bieniasz, a virologist at the Rockefeller University. "It's going to be, over time, likely chipping away at vaccine efficacy, but we're not going to fall of a cliff tomorrow."
Such misbehavior wasn't expected from a coronavirus, which has always been thought of as relatively stable, Sigal said.
"This virus really showed us it can adapt, and could be able to escape," he said. "It just goes back to the first rule of virology: don't underestimate your virus."