Through May 31, Oregon Health Authority has identified 1,009 COVID-19 vaccine breakthrough cases. In May, there were 16,097 cases of COVID-19 and 98 percent of these cases were among people who were unvaccinated. More than 9 in 10 of the 126 COVID-19 associated deaths in May were among people who were not vaccinated. The majority of vaccine-breakthrough associated deaths have occurred in the elderly. The number of vaccine breakthrough cases identified in Oregon remains very small when compared to the more than 1.85 million people who have completed their COVID-19 vaccination series. Vaccine breakthrough cases are defined as instances in which an individual received a positive COVID-19 test result at least 14 days following the completion of any COVID-19 vaccine series. Of the 1,009 reported vaccine breakthrough cases, approximately 10% (n=101) were observed in individuals who reside in long-term care facilities or other congregate care settings. OHA provides updates on breakthrough cases the first Thursday of each month. The current report for June 2021 can be found here.