By Sumit Saxena
New Delhi, May 2 (IANS): Population genetic analyses of SARS-CoV-2 genomes have indicated that these viruses evolved into two major types (designated L and S), which show nearly complete linkage across the viral strains sequenced till date.
But with mutations, there are other strains of this virus, which may have different virulence. Therefore, it is essential to vaccinate everybody by 2021 before the virus acquires any significant mutation, say experts.
Speaking to IANS, Neha Gupta, consultant, Department of Infectious Disease, Fortis Memorial Research Institute, Gurugram, said that through genomic sequencing of the virus, the researchers have found that Covid-19 is mutating, but most mutations are silent mutations, and very slowly accumulating.
"This looks like good news for the success of vaccine. So, if we can vaccinate everyone by early 2021, it can build up protective immunity for a couple of years before the virus acquires another significant novel mutation," Gupta said.
Citing US health advisor Anthony Fauci, she said the vaccine may be available by September 2020, but the accessibility to the vaccine may be an issue.
"We know about L&S strains of novel coronavirus. But, now we know that with mutations, there are various other strains, which have different virulence," added Gupta.
Coronaviruses have been causing problems for a long time and their several versions have been known to trigger common colds. Recently, two types have set off outbreaks of deadly illness: Severe acute respiratory syndrome (Sars) and Middle East respiratory syndrome (Mers).
But, their impact has been placid compared to the menace let loose by the SARS-CoV-2, which led to the Covid-19 pandemic.
Responding to a query on how long the protection will last, Neha Rastogi Panda, Senior Resident, Infectious Disease, Department of Medicine & Microbiology, AIIMS, said that it is another big unknown.
"The recent comments published in the Lancet Journals state that the best estimate comes from the closely related coronaviruses and suggests that, in people who had an antibody response, immunity might wane, but it is detectable beyond one year. Immunity against Mers coronavirus, however, can be detectable for four years," said Rastogi.
She added that human interventions play an important role to select out strains. It can probably become less aggressive (S-type) over the period of time. However, considering the novelty of this virus and the rate of mutations, it is still unknown and unpredictable.
Citing the study, 'On the origin and continuing evolution of SARS-CoV-2', published in the National Science Review (Oxford Academic), Panda added that the more aggressive L type of coronavirus was found more in the early stages of Wuhan outbreak, but its frequency decreased due to human intervention.
"The L type might be more aggressive and spread more quickly. On the other hand, the S type, which is evolutionarily older and less aggressive, might have increased in relative frequency due to relatively weaker selective pressure," added Panda