NEW DELHI: A new study has suggested that only those vaccines which are able to provide protection against multiple variants of the virus can bring the Covid-19 pandemic to an end.
The study underlines that coronavirus has the potential to evade natural as well as vaccine-induced immunity.
Researchers associated with the University of Pennsylvania in the US have concluded that SARS-CoV-2 with mutated forms of the spike protein may retain the ability to bind ACE2 while evading recognition by antibodies that arise in response to the original wild-type form of the spike protein.
It seems likely that immune evasion will be possible regardless of whether the spike protein was encountered in the form of an infectious virus, or as the immunogen in a vaccine.
“Therefore, it also seems likely that reinfection with a variant strain of SARS-CoV-2 may occur among people who recover from Covid-19, and that vaccines with the ability to generate antibodies against multiple variant forms of the spike protein will be necessary to protect against variant forms of SARS-CoV-2 that are already circulating in the human population,” they have said in a scientific paper.
Various vaccines that have been developed to counter SARS CoV 2 have been designed keeping its various variants in mind but there is also a group of clinicians and virologists who believes that those once exposed to the virus may have lasting immunity against it and may not need vaccination.
The researchers, on the other hand, have stressed that mutated forms of SARS-CoV-2 may be able to reinfect people who have recovered from an earlier infection.
Natural infection would tend to generate multiple antibodies to distinct aspects of the spike protein, and immune evasion by mutation becomes increasingly unlikely as the number of independent neutralizing antibodies increases, especially since SARS-CoV-2 has a relatively low genetic diversity, they have said.
However, nearly all of the mutations were identified multiple times on different continents, presumably in the absence of evolutionary pressure, suggesting that they represent “hotspots” where the mutation is spontaneous and frequent.
The paper also said that vaccines containing only one variant of the spike protein as an immunogen may induce little or no protection against variant strains that are already circulating among highly mobile human populations.
An inability to protect against variant strains may severely limit the strategic benefit of vaccines containing only the original strain, it said adding that to have long-term efficacy against SARS-CoV-2 it may be necessary for vaccines to include multiple variants of the spike protein as immunogens.
This strategy is routinely applied against influenza, and all formulations in recent years have all included three or four variant strains. In the case of influenza, however, it has been possible to predict which strains will become epidemic, and the antigenic features of those strains tend to be stable for a season.
“SARS-CoV-2 differs in that many variant strains are already circulating, and their antigenic features are not stable,” the scientists have concluded.