New Study Shows One Dose Of COVID-19 Vaccine Is Not Enough To Protect Against Delta Variant

CHICAGO (CBS) -- There are new concerns Thursday about the fast-spreading COVID-19 Delta Variant and a rise in COVID cases in Illinois and Indiana.

Thursday brought 617 new cases in Illinois -- the most since June 4. In Indiana there were 463 new cases, which is the highest number in three weeks.

And one dose of vaccine will give almost no protection against the highly contagious Delta Variant. A new study out Thursday in the Journal of Nature found that a single dose of Pfizer or AstraZeneca vaccine provides either weak or no protection at all against the variant.

An infectious disease doctor at the University of Chicago said that is one reason there are huge surges in areas with low vaccination rates.

"People have this false belief that it's not the real deal until they see, you know, 20- and 40-year-olds getting lung transplants after having COVID. It doesn't strike home," said Dr. Kathleen Mullane.

The new study also found two doses of the vaccine provide strong protection against the highly contagious variant.

Right now there are more than a million people in Chicago who are not fully vaccinated.