Delta coronavirus variant spreading in unvaccinated pockets of US

Early evidence suggests that the highly contagious delta variant, which has prompted concern worldwide as it leads to new surges of Covid-19 across the globe, is spreading in undervaccinated pockets of the United States.

The genomics firm Helix analysed about 20,000 samples from Covid-19 tests across more than 700 US counties. It found that cases of the variant first documented in India appear to be growing far faster in counties with lower vaccination rates than in areas that have higher rates.

The ongoing spread of the variant in pockets of low vaccine uptake are troubling because they create more opportunities for the virus to thrive and mutate. The longer the virus spreads, the more chances it has to create easier inroads into human cells, and potentially take on deadlier forms.

“Delta is driving surges around the world, and I suspect it’s going to be the same here,” said William Lee, the vice-president of science at Helix. Delta is growing more than twice as fast as gamma, the variant first seen in Brazil, in undervaccinated communities.

Meanwhile, the Gamma variant, which appears better at evading vaccines, was found to be more prevalent in counties with higher inoculation rates. The Helix research, which hasn’t yet been subject to peer review, is to be published in an upcoming preprint online.

So far, more than 45 per cent of the US population has been fully vaccinated, according to the Centres for Disease Control and Prevention. But a recent Bloomberg News analysis found that broad, national numbers often obscure more troubling patterns at the local level.