What is the new strain of coronavirus?
After the UK became the first country to start vaccinating its citizens, the emergence of a new strain of the coronavirus has raised the alarm. In recent weeks, authorities have detected a sharp rise in a highly contagious variant of Covid-19 in southeast England and London. Plans to further ease restrictions for the holiday season were put on hold when the government imposed the strictest lockdown to date, confining millions to their homes.
More than 20 mutations are contained in this new strain, or variant, of Covid-19, which is unprecedented. But mutations themselves are not uncommon: the coronavirus has mutated at a rate of one to two times a month since its genetic code was sequenced in January, and most mutations have had little real impact on the virus and its characteristics. .
The reason this strain stands out is because eight of the mutations are related to the gene responsible for the spike protein. In particular, two are of concern: the N501Y mutation, which can make the virus more effective in invading cells, and the H69 / V70 deletion mutation, which can hamper the immune response in some immunosuppressed patients. Anecdotal data suggests that this strain could spread faster and cause more serious disease.
But much is still unknown about this mutated version of the virus, called B.1.1.7. Although officials have said that the new variant is 70% more transmissible, this figure is based on models not confirmed by laboratory experiments. Already several countries, including India, have banned travel to and from the UK.
Why mutations occur
A virus spreads by making copies of itself. But copies are not always exact replicas, and errors creep into the process. More complex viruses may have a “proofreading” mechanism to check for these replicas. But the mechanism is not as well developed in RNA viruses, such as Sars-CoV-2, and therefore mutations.
So far, multiple strains of Sars-CoV-2 have been identified worldwide, but there are no marked variations in their behavior. For a virus, most mutations do not cause any substantial change and are called “neutral”. But mutations can also occur that make it less effective. The strains thus created do not infect people and eventually die. But the concerning mutation is one that may allow the virus to spread more effectively.
An information display board in London. The UK Prime Minister has announced a ‘stay at home’ order for London and South East England to curb a new strain of coronavirus
How will the new strain affect vaccines?
If the new mutation is considered capable of driving an increase in cases, it is likely due to the change it produces in the coronavirus spike protein, which is what the virus uses to adhere to and enter healthy cells.
The spike protein is critical to the Pfizer and Moderna vaccines that have so far been approved against coronavirus in the US and UK. These are designed to teach the human immune system to recognize these spike proteins and create antibodies that can prevent the virus from infecting cells.
But if the mutation changes the spike protein itself, will these vaccines still be effective? Experts have reason to believe that they still will. This is because it is rarely the case that a single significant mutation produces a dramatic change in the way a virus attacks humans.
The Pfizer and Moderna vaccines can be easily modified to accommodate changes in Sars-CoV-2
Viruses are known to escape immunity, that is, to defeat antibodies and vaccines, the best known example being the seasonal flu virus. But the vaccines themselves can be updated to account for the changes, which means they continue to be effective with slight adjustments. The good news about Pfizer, Moderna vaccines is that they can be easily modified to match the changes in Sars-CoV-2.
Furthermore, to escape immunity, a virus must assume a series of mutations. The influenza virus, which changes fairly rapidly, still takes five to seven years to change enough to overcome immune recognition.
Mutation is the norm for viruses and will almost certainly occur with Sars-CoV-2 as more people recover from the disease and vaccination further boosts immunity, but experts say immunity for about 60 % of the population in a year while maintaining the case count could greatly reduce the possibility of the virus mutating.
Will India’s vaccine strategy be affected?
India’s vaccine strategy is unlikely to be affected as vaccines being developed are expected to be effective against the new strain and reinfections, if they occur, would be milder, according to experts. The candidate vaccines under regulatory evaluation in India included injections with various other components in addition to the spike protein, which is related to this particular strain, and this would help the vaccines maintain their efficacy.
Epidemiologists in India say that mutations are common to viruses and that people should continue to wear masks and maintain physical detachment and hand hygiene. “There is no reason to worry from now on. Each virus changes its genetic makeup. This virus has a very low mutation rate, “said lead epidemiologist Dr. Raman Gangakhedkar, former chief scientist at the Indian Council for Medical Research.
Source: Science Magazine, NYT, media reports
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