Delta variant: How transmissible is the COVID variant spreading in the UK and elsewhere?

Despite a strong vaccination programme, the UK has had to put plans for a full re-opening of its economy on hold, as the Delta variant of COVID — first identified in India — has quickly become the dominant variant in the country.

Data from Public Health England reveals how the rise in Delta cases in England has far outstripped any previous variant that has been identified — suggesting it is substantially more transmissible. Estimates currently peg the R0 (reproduction number) for the Delta variant between 5 and 8, compared to an R0 of about 3 for the variant that caused Europe's first wave.

That may sound concerning, but the latest data also suggests that vaccinations are still highly effective at preventing hospitalizations for those who catch the Delta variant. 2 doses of the Pfizer-BioNTech vaccine were found to be 96% effective against hospitalizations for Delta, and 2 doses of the Oxford-AstraZeneca vaccine were found to be 92% effective.

In the US, Delta cases remain more sparse, but are reportedly doubling roughly every 2 weeks. Acknowledging the potential threat from Delta, the CDC labelled the Delta strain a "variant of concern" this week.