The newer Omicron sub variants of SARS-CoV-2 substantially escape neutralising antibodies induced by both vaccination and previous infection, according to a study published in the New England Journal of Medicine.
The study provides the immunologic context for current surges among populations with high rates of vaccinations and previous infection, the researchers said.
Since the initial highly infectious SARS-CoV-2 Omicron variant -- known as BA.1 -- of Covid-19 emerged last year, its new subvariants continue to evolve.
The researchers from Beth Israel Deaconess Medical Center (BIDMC) in Israel evaluated antibody response to multiple SARS-CoV-2 Omicron subvariants in 27 vaccinated and boosted individuals and 27 individuals who had previously contracted Covid-19.
They found that the three Omicron subvariants BA.2.12.1, BA.4, and BA.5 substantially escape neutralising antibodies induced by both vaccination and previous infection.
Neutralising antibody responses to BA.4 and BA.5 were approximately 20-fold lower than to the original WA1/2020 strain and were 3-fold lower than to the Omicron BA.1 and BA.2 variants.
"Our findings suggest that the Omicron variants have continued to evolve," said study senior author Dan H Barouch, director of the Center for Vaccine and Virology Research at BIDMC.
"This has important public health implications and provides the immunologic context for current surges among populations with high rates of vaccinations and previous infection,” Barouch said.
The researchers noted that new variants that emerge may be more transmissible and may more effectively bypass the immune protection from prior infection or vaccination.
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