A new analysis has shown how the COVID-19 Delta variant became the dominant, hardly challenged strain of the virus.
The SARS-CoV-2 B.1.617.2 – Delta – variant first spread throughout India, becoming the most widespread variant and replacing the Alpha and Kappa variants.
It has been shown to be six times less sensitive to neutralising antibodies from individuals who have recovered from infection, and eight times less sensitive to vaccine-elicited antibodies, than the original strain which spread from Wuhan.
In tests, the Delta variant "demonstrated higher replication efficiency in both airway organoid and human airway epithelial systems", reported scientists in Nature on Monday.
Their analysis of over 130 infected health care workers at three centres in India found reduced effectiveness for the Oxford AstraZeneca vaccine against the Delta variant relative to other strains.
"Compromised vaccine efficacy against the highly fit and immune evasive B.1.617.2 Delta variant warrants continued infection control measures in the post-vaccination era," they warn.
Senior author, Professor Ravi Gupta of the University of Cambridge, UK, said: “By combining lab-based experiments and epidemiology of vaccine breakthrough infections, we’ve shown that the Delta variant is better at replicating and spreading than other commonly-observed variants.
"There’s also evidence that neutralising antibodies produced as a result of previous infection or vaccination are less effective at stopping this variant.
“These factors are likely to have contributed to the devastating epidemic wave in India during the first quarter of 2021, where as many as half of the cases were individuals who had previously been infected with an earlier variant.”
Co-author Professor Anurag Agrawal added: “We urgently need to consider ways of boosting vaccine responses against variants among health care workers.”
Mlcochova, P. et al. SARS-CoV-2 B.1.617.2 Delta variant emergence and vaccine breakthrough. Nature 6 September 2021; doi: 10.1038/s41586-021-03944-y
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