The Delta variant of the coronavirus may be substantially better than past strains at infecting fully vaccinated people, officials in Israel warned Monday. However, their conclusions have yet to be vetted by outside scientists, and vaccinated people still remain very well protected against more serious illness and death from the variant.
According to the Israel Ministry of Health, their analysis of recent case data (collected from June 6 to early July) suggests that the Pfizer/BioNTech vaccine is only around 64% effective at preventing any infection from Delta in the fully vaccinated, meaning both symptomatic and asymptomatic cases — a sharp contrast from the 94% effectiveness from infection found with earlier versions of the virus. The vaccine’s effectiveness against serious illness and hospitalisation also appeared to decline, but only slightly, the health ministry added. They estimated the Pfizer vaccine was 94% effective at preventing serious illness from Delta, compared to 98% previously.
Delta is more transmissible than past strains of the coronavirus, including earlier variants that were themselves more transmissible than the strains that kickstarted the pandemic early last year. These findings are not the first to indicate that Delta is also more of a challenge for an immune system trained to recognise the wild-type strains of the virus that circulated throughout the world last year (and that all currently available vaccines are based on). Lab data has indicated, for instance, that the immune systems of vaccinated people produce fewer antibodies capable of effectively neutralising Delta than they do against the wild type, and it’s these antibodies that play a large role in preventing infection from taking place at all.