US data show rising 'breakthrough' infections among fully vaccinated

CHICAGO - Some 25% of SARS-CoV-2 infections among Los Angeles County residents occurred in fully vaccinated residents from May through July 25, a period that includes the impact of the highly transmissible Delta variant, U.S. officials reported on Tuesday.

The data, published in the U.S. Centers for Disease Control and Prevention's weekly report on death and disease, shows an increase in so-called "breakthrough" infections among fully vaccinated individuals. The CDC is relying on data from cohorts, such as the Los Angeles County study, to determine whether Americans need a third dose of COVID-19 vaccines to increase protection. Government scientists last week laid out a strategy for booster doses beginning on Sept. 20, pending reviews from the U.S. Food and Drug Administration and the CDC.