Virus ‘Endemic,’ Expect More Variants, Vaccine Tweaks

Virus ‘Endemic,’ Expect More Variants, Vaccine Tweaks

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After a new, potentially more easily transmissible genetic variant of SARS-CoV-2 was reported in the United Kingdom, several scientists have said that current vaccines are likely to protect against the new variant, and vaccine manufacturers are running tests to make sure.

But as a larger proportion of the global population becomes immune to SARS-CoV-2 through infection or vaccination, the virus will likely evolve to escape that immunity, and vaccines may need to be updated, Edward Holmes, PhD, told Medscape Medical News.

“I can’t predict what mutations will appear in what order at what time, but I can make a pretty sure prediction it’s going to evolve and escape immunity like everything always does,” said Holmes, an evolutionary virologist at the University of Sydney, Sydney, Australia, who was involved in mapping the SARS-CoV-2 genome. “That’s an inevitable consequence of natural selection. It’s been played out for millennia and will happen again.”

Research will show whether current vaccines are still highly effective against the newly reported variants. If they are, “we can breathe a small sigh of relief,” Holmes told Medscape Editor-in-Chief Eric Topol, MD, leader of the Scripps Translational Science Institute in La Jolla, California, in an upcoming episode of One-on-One Interviews. Other virologists and vaccinologists have tweeted in recent days that they anticipate that the new variant is likely not sufficiently different to make current vaccines ineffective.

New Variant of an “Endemic” Virus

The UK variant of SARS-CoV-2, named lineage B.1.1.7, has a large number of genetic differences, particularly in the virus’ spike protein, according to scientists who authored a preliminary genomic characterization of the variant. They identified three mutations with potential biological effects: N501Y, which changes an amino acid in the spike protein’s receptor binding domain; the deletion of two amino acids in the spike at sites 69–70; and another amino acid change, P681H.

The variant appears to be growing rapidly in the United Kingdom, Holmes said, because the new lineage is increasing in frequency compared to others. The same phenomena appears to be occurring in South Africa, where a different genetic lineage with the N501Y mutation is spreading, Minister of Health Zwelini Mkhize, MBCHB, announced on December 18.

There’s evidence that viral loads are heavier in people infected with the UK variant, as indicated by lower average cycle threshold values for PCR tests and more sequence reads when samples are sequenced, Holmes said. This would explain the new variant’s faster growth.

Previous research has shown the N501Y mutation in the spike protein is critical for host-cell receptor binding. That mutation provides a molecular explanation for the observed higher viral loads in infected patients, Holme

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