What is breakthrough disease and why is it happening with COVID-19?


Why do people who have been vaccinated against COVID-19 sometimes get the disease?


Sometimes when people are immunized against a vaccine preventable disease they still get the disease. This is called "breakthrough" disease or a breakthrough case. It happens when a person who has been fully vaccinated becomes infected with the coronavirus. No vaccine is 100% effective and the greater the proportion of people vaccinated in a population, the greater the proportion of cases will occur among vaccinated people. However, the overall number/incidence of cases will be way lower than without vaccination, and the severity of illness among vaccinated people (including hospitalization and death) is lower. Watch this informative video from the World Health Organization that explains more fully why some people will get breakthrough disease. 




Date last reviewed: 
Friday, Aug 20, 2021