Vaccine effectiveness against COVID-19 infection dropped from 91% to 66% once the delta variant accounted for the majority of circulating virus, according to a study published Tuesday by the U.S.

Alexander Tin is a digital reporter for CBS News based in the Washington, D.C. bureau. He covers federal public health agencies. "Looking at cases over the past two months when the Delta variant was ...

Those are the words from CDC director Dr. Rochelle Walensky in a recent interview with Scripps National Correspondent Dan Grossman. It can be a startling confession to hear, but one Dr. Walensky ...

The more contagious Delta variant of Covid-19 now makes up 83% of sequenced samples in the United States, US Centers for Disease Control and Prevention Director Dr. Rochelle Walensky said Tuesday.

ATLANTA, Ga. — The delta variant that’s now the dominant strain of coronavirus in the U.S. appears to be as transmissible as chickenpox, according to an internal document from the Centers for Disease ...

LAS VEGAS, NEVADA -- A California couple says they were fully vaccinated, but still contracted COVID-19 while on vacation as experts say breakthrough cases are possible, especially with the delta ...