NEW DELHI: Indian double mutant B.1.617 was classified as variant of global concern (VOC) by the World Health Organisation (WHO) on Monday. But a study by scientists from the UK and India shows that it has moderate antibody resistance and is unlikely to be a major immune escape variant though it has higher infectivity but low severity for vaccinated individuals.
A paper ‘SARS-CoV-2 B.1.617 emergence and sensitivity to vaccine-elicited antibodies’ by experts at Cambridge University, the National Centre for Disease Control, Delhi and CSIR Institute of Genomics and Integrative Biology (IGIB) show that vaccinated individuals can be infected with B.1.617, but without severe disease.
The B.1.617 spike bearing L452R, E484Q, and P681R has a modest ability to avoid neutralising antibodies elicited by vaccination. The fold reduction for the two mutations L452R and E484Q was no greater than the individual mutations alone, arguing against the use of the term ‘double mutant’, said the paper in pre-prints.
“First molecular insights into B.1.617 VOC by collaboration of INSACOG and Cambridge University. Only moderate antibody resistance but greater syncytium formation. Overall fits higher transmissibility, symptoms, but low severity in vaccinated,” said Anurag Agrawal, Director, IGIB.
The loss of neutralisation of B.1.617 has likely contributed to an epidemic wave in India where background infection to the Wuhan-1 D614G in 2020 was between 20-50%. Despite in vitro data showing only a small loss of neutralisation against B.1.617 with the Covaxin vaccine, here we also show vaccine breakthrough in health care workers at a single tertiary hospital who were fully vaccinated.
“These infections were predominantly B.1.617, with a mix of other lineages bearing D614G in spike. The dominance of B.1.617 could be explained by the prevalence of this lineage in community infection or simply reflect transmission between HCWs. The data nonetheless raise the possibility of a transmission advantage of B.1.617 in vaccinated individuals,” it said.
The experts say that vaccinated individuals can be infected with B.1.617, but without severe disease. The data go some way to explaining the dominance of this variant in a partially immune population, but highlight that vaccination is still protective for the majority of people.
“It is unclear whether B.1.617 variants will prove more transmissible than B.1.1.7, also circulating in India and now globally dominant. In the absence of published data on the transmissibility of B.1.617 we predict that this variant will have a transmission advantage relative to Wuhan-1 with D614G in individuals with pre-existing immunity from vaccines/natural infection as well as in settings where there is low vaccine coverage and low prior exposure,” it added.
The paper says that lower protection against B.1.351, the variant with the least sensitivity to neutralising antibodies, has been demonstrated for at least three vaccines.
“However, progression to severe disease and death was low in all studies. Therefore, at population scale, extensive vaccination will likely protect against moderate to severe disease and will reduce transmission of B.1.617 given the in vitro neutralisation data we and others have presented,” it further said.