Delta coronavirus variant spreading fast in California

LOS ANGELES — Delta is now the variant of the coronavirus identified third most often in California, according to new data — underscoring that the variant is highly contagious, a danger to people who have not been vaccinated against COVID-19.

The Delta variant now makes up 14.5% of California coronavirus cases analyzed so far in June, up from 4.7% in May, when it was the fourth-most-identified variant in California, according to data released by the California Department of Public Health.

Experts say the Delta variant poses a greater chance of infection for unvaccinated people if they are exposed to this version of the virus. The variant, first identified in India, may be twice as transmissible as the conventional coronavirus strains. The Delta variant has been responsible for the rise in cases recently in India, the United Kingdom and elsewhere.

But vaccinated people are well protected against infection and illness from the Delta variant. One recent study found that the full course of the Pfizer-BioNTech vaccine (two doses) was 88% effective against symptomatic disease caused by the Delta variant and 96% protective against hospitalization.

There is no widespread scientific consensus on whether the Delta variant is more likely to cause more serious illness than other conventional strains.

Delta’s rise comes as California’s currently dominant strain, Alpha, first identified in the United Kingdom, may have peaked.

In May, the Alpha variant comprised 58.4% of coronavirus cases that were analyzed in California. In June, Alpha’s share fell, and now makes up 37.7% of analyzed cases — still the top variant but with a much smaller percentage among all variants sequenced.