The COVID-19 vaccine can cause people to develop COVID-19.

As of January 2021, none of the vaccinations approved for broad use in the United States or Europe include the live virus that produces COVID-19 virus. "This implies that a COVID-19 vaccination cannot get you sick with COVID-19", according to the Centers for Disease Control and Prevention. The CDC did emphasize, however, that the existing vaccinations require two doses, and that it will take some time for the body to develop antibodies against the COVID-19 virus following immunization. "This implies that a person might be infected with the virus that causes COVID-19 shortly before or immediately after immunization and still become unwell", according to the CDC. "This is because the vaccination did not have enough time to protect."

COVID-19 instances in fully vaccinated people are still conceivable since none of the existing vaccinations have been shown to be 100 percent effective in preventing symptomatic COVID-19 cases. According to the Children's Hospital of Philadelphia, the immunizations may not prevent asymptomatic infection, which means that vaccine recipients may become sick, exhibit no symptoms, and unknowingly spread the virus.