What is a COVID-19 vaccine 'breakthrough' case?

A COVID-19 vaccine “breakthrough” case is when a vaccinated person gets infected with the coronavirus

What is a COVID-19 vaccine “breakthrough” case? It’s when a fully vaccinated person gets infected with the coronavirus. In studies, the two-dose COVID-19 vaccines by Pfizer and Moderna were around 95% effective at preventing illness, while the one-shot Johnson & Johnson shot was 72% effective, though direct comparisons are difficult. So while the vaccines are very good at protecting us from the virus, it’s still possible to get infected with mild or no symptoms, or even to get very sick. If you do end up getting sick despite vaccination, experts say the shots help reduce the severity of the illness — the main reason to get vaccinated.