How COVID vaccines work against the Delta variant

The Delta variant of coronavirus is a source of serious concern as lab tests have shown it is more contagious and resistant to vaccines compared with other forms of COVID-19. However, there is evidence that the available jabs retain important effectiveness against it after two doses. A British study published in The Lancet medical journal in early June looked at levels of neutralising antibodies produced in vaccinated people exposed to the Delta, Alpha (first identified in Britain) and Beta (first identified in South Africa) variants. It found that antibody levels in people with two doses of the Pfizer-BioNTech shot were six times lower in the presence of the Delta variant than in the presence of the original COVID-19 strain on which the vaccine was based. The Alpha and Beta variants also provoked lower responses, with 2.6 times fewer antibodies for Alpha and 4.9 times fewer for Beta.