https://www.nationalreview.com/news/less-than-0-01-percent-of-vaccinated-americans-developed-severe-covid-breakthrough-case-cdc-says/

"As of August 2, more than 164 million people have been fully inoculated against the disease, CDC numbers indicate. Less than 0.01 percent of this population have suffered severe or fatal cases of COVID when they contracted it post-vaccination. Since the vaccine’s distribution, the agency has received reports of 7,525 patients with COVID-19 vaccine breakthrough infections who were hospitalized or died."

https://www.cdc.gov/vaccines/covid-19/health-departments/breakthrough-cases.html

"As of August 23, 2021, more than 171 million people in the United States had been fully vaccinated against COVID-19."

"During the same time, CDC received reports from 49 U.S. states and territories of 11,050 patients with COVID-19 vaccine breakthrough infection who were hospitalized or died."

11,050 / 171,000,000 = 0.00007 ish.