The Delta Variant Is a Grave Danger to the Unvaccinated
Lineage B.1.617.2, now known as the Delta variant, was first detected in India, in December, 2020. An evolved version of sars-CoV-2, Delta has at least a dozen mutations, including several on its spike protein that make it vastly more contagious and possibly more lethal and vaccine-resistant than other strains. In India, the Delta variant contributed to the most devastating coronavirus wave the world has seen so far; now it has been detected in dozens of countries, including the United States. In the U.S., it accounts for a minority of cases—but it is rapidly outcompeting other variants, and will likely soon become our dominant lineage.
Much of what we know about Delta is preliminary, and based on reports from India and, more recently, the U.K., where it now accounts for more than ninety per cent of new cases. Four-fifths of British adults have received at least one shot of a covid-19 vaccine, and more than half are fully vaccinated—but the variant has spread widely enough among those who remain vulnerable to fuel a quadrupling of cases and a doubling of hospitalizations in the past month. The vast majority of Delta-variant cases seem to have occurred in adults under fifty, whose rates of vaccination remain lower than those of older people. Last week, Prime Minister Boris Johnson announced that the U.K.’s full reopening, originally scheduled for June 21st, would be postponed.
Earlier this year, scientists estimated that lineage B.1.1.7—the Alpha variant, first isolated in England—could be some sixty per cent more transmissible than the original version of sars-CoV-2. Now experts believe that the Delta variant is sixty per cent more transmissible than Alpha—making it far more contagious than the virus that tore through the world in 2020. It hasn’t yet been conclusively shown that Delta is more lethal, but early evidence from the U.K. suggests that, compared to Alpha, it doubles the risk of a person’s being hospitalized. Even if the variant turns out to be no deadlier within any one person, its greater transmissibility means that it can inflict far more damage across a population, depending on how many people remain unvaccinated when it strikes.
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