EYECARE: Coronavirus BRIEFING: Crisis Response Tactics CDC: COVID-19 Vaccines 66 Percent Effective Against Delta Variant By Staff Thursday, August 26, 2021 8:03 AM Vaccine effectiveness against COVID-19 infection dropped from about 91 percent to 66 percent once the Delta variant became the dominant strain in the U.S., according to a new study published Tuesday by the CDC.The decline points to the highly contagious nature of the Delta variant and underscores the importance of vaccination to prevent severe disease, hospitalization, and death, the study authors wrote.“While we did see a reduction in the protection of the COVID-19 vaccine against the Delta variant, it’s still two-thirds reduction of risk,” Ashley Fowlkes, ScD, the lead author and an epidemiologist for the CDC’s COVID-19 Emergency Response, told CNN. Head over to WebMD to read the full story.