Scientists have assessed the course of evolution of the novel coronavirus 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 study, published in the journal Virus Evolution, assessed whether, over the long term, the SARS-CoV-2 virus is likely to demonstrate an immune evasion capability on par with that of influenza viruses.
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, 229E and 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.
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.
Frequently Asked Questions
A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.
There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.
Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.
"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.
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.