A study in Washington state (https://www.doh.wa.gov/Portals/1/Documents/1600/coronavirus/data-tables/420-339-VaccineBreakthroughReport.pdf?) gathered data from over 4 million fully vaccinated people. The data showed a rate of about 1 in 5,000 experienced a breakthrough infection between January 17 and August 21, 2021. More recently, some populations have shown breakthrough infection rates of approximately 1 in 100 fully vaccinated people.