The Washington State Department of Health (DOH) announced Tuesday it is investigating reports of people who tested positive for COVID more than two weeks after being fully vaccinated against the disease. According to Kiro 7 News, a CBS affiliate in Washington, the DOH is investigating reports of the so-called “breakthrough cases,” which it said are expected with any vaccine. Each case was confirmed with a polymerase chain reaction (PCR) test or a positive antigen test more than two weeks after the person had been fully vaccinated. A majority of people with confirmed vaccine breakthrough experienced mild symptoms, if any. However, since Feb. 1, eight people with vaccine breakthrough cases were hospitalized and the DOH “is investigating two potential vaccine breakthrough cases where the patients died. Both patients were more than 80 years old and suffered underlying health issues,” officials said in a press release.