Oregon Health Authority has identified 168 COVID-19 vaccine breakthrough cases â when vaccinated individuals test positive for the virus â thru April 2, including three deaths. OHA public health officials say itâs a reminder that while the Pfizer, Moderna and Johnson & Johnson COVID-19 vaccines are all highly effective at preventing severe COVID-19 illness and death, no vaccine is 100% effective, and vaccine breakthrough cases will occur. These cases have been reported in 25 counties and all health care preparedness regions (Region 1: 76; Region 2: 29; Region 3: 27; Region 5: 9; Region 6: 4; Region 7: 17; Region 9: 6). OHA is not reporting the regions in which the deaths took place. Vaccine breakthrough cases are defined as instances in which an individual received a positive COVID-19 test result at least 14 days after the final dose of any COVID-19 vaccine series. Vaccine breakthrough cases can be prevented by basic public health interventions, such as masking, physical distancing and avoiding social gatherings.