Relative to vaccinated people, those who are unvaccinated and infected with COVID-19 face a 10 times higher risk of hospitalization and are 11 times more likely to die from the disease, the CDC's Sept. 10 Morbidity and Mortality Weekly Report found.
"Looking at cases over the past two months when the delta variant was the predominant variant circulating in this country, those who were unvaccinated were about four and a half times more likely to get COVID-19, over 10 times more likely to be hospitalized and 11 times more likely to die from the disease," Rochelle Walensky, MD, CDC director, said of the study's results during a Sept. 10 news conference.
Researchers analyzed rates of COVID-19 cases, hospitalizations and deaths among adults across 13 U.S. jurisdictions from April 4 to July 17, 2021.
The report showed that as the highly transmissible delta variant became more prevalent in the U.S., the risk of breakthrough cases also rose, though the vaccines were effective in preventing severe illness.
From April 4 to June 19, when delta prevalence was lower, fully vaccinated people accounted for 5 percent of COVID-19 cases, 7 percent of hospitalizations and 8 percent of deaths, overall.
When delta prevalence was higher from June 20 to July 17, vaccinated people accounted for 18 percent of cases, 14 percent of hospitalizations and 16 percent of deaths.
"Rates of COVID-19 cases, hospitalizations, and deaths were substantially higher in persons not fully vaccinated compared with those in fully vaccinated persons, similar to findings in other reports," the CDC said.