Delta variant’s agility is unmatched, but not invincible

The delta variant is driving COVID-19's surge in Washington and nationwide.

Delta (officially "B.1.617.2") spreads quickly and multiplies within an infected person’s body more efficiently than its predecessors, says UW Medicine virologist Dr. Alex Greninger.

“When viruses are good at transmitting between people, they actually sort of win races within an individual,” he says.  People infected with the delta variant often have higher viral loads (particles of virus) than those carrying other SARS-CoV-2 strains.

Delta now represents more than 80% of all U.S. COVID-19 cases, a mark reflected in UW Medicine's dashboard of sequenced results from Washington-based tests (81.3% on July 4).

Despite delta’s maneuverability, new research shows the vaccines approved for emergency use provide adequate protection. Breakthrough cases are well-reported but at this time only a slim possibility, data suggests.

Vaccines work "great for preventing severe disease and hospitalizations, even preventing symptomatic cases,” Greninger says.