Scientists have assessed the course of evolution of seasonal human coronaviruses (HCoV) and predicted that COVID-19 vaccines currently in use across the world may need regular updates to counter new variants of the virus which are capable of escaping the body's protective antibodies.
The results were published in the journal Virus Evolution.
In the research, virologists from Charite-Universitatsmedizin Berlin in Germany studied the genetic evolution of the four currently known 'common cold' coronaviruses, particularly the two longest-known viruses, HCoV-229E and HCoV-OC43. They traced changes in the spike protein of the these coronaviruses, which enable them to enter host cells, approximately 40 years into the past.
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Based on the analysis, the scientists found one feature which was common to both the coronaviruses and the influenza virus — all three had a pronounced ladder-like shape in their evolutionary paths.
"An asymmetrical tree of this kind likely results from the repeated replacement of one circulating virus variant by another which carried a fitness advantage," explained the study's first author, Wendy K. Jo.
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According to Jo, this is evidence of 'antigenic drift', a continuous process involving changes to surface structures which enable viruses to evade the human immune response. "It means that these endemic coronaviruses also evade the immune system, just like the influenza virus. However, one also has to look at the speed with which this evolutionary adaptation happens," she added.
The scientists said the novel coronavirus genome is currently estimated to change at a rate of approximately 10 mutations per 10,000 base molecules per year, meaning the speed at which it evolves is substantially higher than that of the endemic coronaviruses.
"This rapid genetic change in SARS-CoV-2 is reflected in the emergence of numerous virus variants across the globe," explained study co-author Jan Felix Drexler. "This, however, is likely due to the high rates of infection seen during the pandemic. When infection numbers are so high, a virus is able to evolve more rapidly," Drexler added.
Based on the rates of evolution seen in the endemic common cold coronaviruses, the scientists believe SARS-CoV-2 will start to change more slowly once infections start to die down.
"Once a large proportion of the global population has developed immunity either as a result of infection or through vaccination. We expect therefore that COVID-19 vaccines will need to be monitored regularly throughout the pandemic and updated where necessary," Drexler explained.
According to the virologists, vaccines are likely to remain effective for longer once the pandemic reaches this stable situation.
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