‘There's always new strains, that's what bugs do’: USC doctor on Delta variant spreading fast

The delta variant of COVID-19 was first identified in India and is now surging in the United Kingdom and South Africa, where travel restrictions have been eased. Israel, which has the highest percentage of vaccinated residents, also faces a delta variant outbreak, but they’re not imposing any shutdown orders.  

In California, the delta variant accounts for nearly 15% of cases, according to the state’s public health department. While vaccinations seem to provide protection, public health officials are increasingly concerned about what this means for unvaccinated people. 

Dr. Edward Jones Lopez of USC’s Keck School of Medicine says although this variant appears to be more infectious and potentially deadlier, it doesn’t necessarily appear to be a major concern for fully vaccinated individuals. 

However, he stresses the importance of receiving both vaccine doses. “Early on, the U.K. strategy of maximizing the number of people with one [vaccine dose] was thought to be a very effective strategy because they were among the countries in Europe with the sharpest decrease in the number of cases. But now this delta variant has been introduced … and it's really spreading very, very quickly. And in part likely because of this strategy of … trying to concentrate on single closes versus two of those.”

He adds that data from other countries is showing that although this strain is causing more cases, very few of those cases involve people who are dying or admitted to the hospital.

Lopez notes that the delta variant results from a natural progression in viruses as they mutate. 

“At the end of the day, we do know it's even more infectious than previous variants ... than the ancestor strain, the original strain that came from China,” he says. “There's always new strains. That's what bugs do. They're always trying to avoid the interventions we developed to stop their spread. And the best way they can do that is changing their genetic material to avoid the effect of vaccines.”



  • Dr. Edward Jones Lopez - MD, MS, assistant professor of medicine at the Keck School of Medicine at University of Southern California; investigator of the AstraZeneca vaccine trial in the U.S.