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Understand COVID-19: Novel Coronavirus Mutations and Variants

Learn more about the Yale School of Medicine's response to COVID-19, visit: Since the beginning of the COVID-19 pandemic, scientists knew it was a matter of time before new variants of the novel coronavirus, SARS-Cov-2, began to emerge in our communities. For a virus that mutates relatively slowly – picking up an average of two to three new mutations a month – how quickly these distinct variants took root would depend on how well we stopped the spread of the virus. Viruses rely on our cellular equipment to reproduce; mutations can only continue if it keeps infecting people. This particular virus gains access to our cells using its “corona” – a layer of protein spikes that fit into our cellular receptors like a lock and key. But, says Akiko Iwasaki, PhD, “When viruses enter the host cells and replicate and make copies of their genomes, they inevitably introduce some errors into the code.” SARS-Cov-2 is an RNA virus. Unlike many other RNA viruses, though, the novel coronavirus has some ability to check for transcription errors as it replicates. Iwasaki, who studies the mechanisms of immune defense against viruses, compares these errors to a faulty spell-checker. Some of these random errors that get passed on are either neutral or detrimental to the virus. But some errors are beneficial to the virus – making it more contagious, for example – and allow it to proliferate and spread to more people. Over time, the cumulative effects of these mutations may be enough to change how the virus behaves. These “better fit” versions of the virus become the “building blocks of selection,” says Nathan Grubaugh, PhD. These constellations of viral mutations – known as variants – may take hold if there is evolutionary pressure for them to do so. But the novel coronavirus is highly contagious and has spread almost unchecked throughout the world for the last year. It remains a bit of a mystery as to why these variants are emerging now – and what it will mean long-term for vaccination programs. Currently, scientists are optimistic that the three main vaccines available in the US – Pfizer, Moderna and Johnson & Johnson – will continue to provide good immunity. “There are certain mutations in some of these variants that seem to decrease the effectiveness of really important antibodies,” says Grubaugh. “But luckily with vaccines, you don’t just create one antibody, or two or three, you create many different antibodies that recognize all different parts of the virus.” “The mRNA technology is very flexible and can accommodate new mutations,” says Iwasaki. And even if the effectiveness of vaccines dropped to, say, 75 or 85 percent, that would still provide important protection and prevent severe cases of the disease that bring people to the emergency room. Questions about the vaccine remain, however, like whether a fully-vaccinated person could still transmit the virus to another person without being sick themselves. That’s why Iwasaki says it’s still important to continue wearing masks, avoid crowds, and practice good hygiene. “We have all the tools needed to stop the transmission and the spread of these new variants,” Grubaugh emphasized. “If we all put a lot of effort into doing our part, these variants won’t be able to take a foothold in our community at all.”
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