The Delta variant has been linked to a resurgence of COVID-19 in Nepal, southeast Asia and elsewhere, but its UK spread has given scientists a clear picture of the threat it poses. Delta seems to be around 60% more transmissible than the already highly infectious Alpha variant identified in the United Kingdom in late 2020.
Delta is moderately resistant to vaccines, particularly in people who have received just a single dose. A Public Health England study published on 22 May found that a single dose of either AstraZeneca’s or Pfizer’s vaccine reduced a person’s risk of developing COVID-19.
Preliminary evidence from England and Scotland suggests that people infected with Delta are about twice as likely to end up in the hospital, compared with those infected with Alpha.
Denmark, which, like the United Kingdom, is a world leader in genomic surveillance, has also seen a steady rise in cases caused by the Delta variant — although far fewer than most other European countries. It is only a matter of time before the variant becomes dominant in Denmark, says Albertsen, but the hope is that its expansion can be slowed through vaccination, surveillance, and enhanced contact tracing. “It’s going to take over,” he says, but “hopefully in a few months and not too soon.”
Meanwhile, the Danish government is easing restrictions, not re-imposing them: restaurants and bars have been open for months to individuals who have been vaccinated or received a recent negative test, and, as of 14 June, masks are no longer required in most indoor settings.
Cases of the Delta variant in the United Kingdom are doubling roughly every 11 days. But countries with ample vaccine stocks should be reassured by the slower uptick in hospital admissions, says Wenseleers. A recent Public Health England study1 found that people who have had one vaccine dose are 75% less likely to be hospitalized, compared with unvaccinated individuals, and those who are fully protected are 94% less likely to be hospitalized.
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