The Centers for Disease Control and Prevention tracks only breakthrough cases that result in hospitalization or death, as these incidences are both serious and very rare.

COVID-19 cases are up to five times more common in unvaccinated individuals compared with the vaccinated, according to the CDC. But state-level data shows that milder breakthrough cases that do not result in hospitalization are on the rise among the fully vaccinated as virus transmission increases and vaccine efficacy decreases.