After a vaccine is authorized for use, many vaccine safety monitoring systems watch for possible side effects. This monitoring can pick up on adverse events that may not have been seen in clinical trials. If an unexpected adverse event is seen, experts study it further to assess whether it is a true safety concern. Experts then decide whether changes are needed in U.S. vaccine recommendations. This monitoring is critical to help ensure that the benefits continue to outweigh the risks for people who receive vaccines.

 

CDC has a new smartphone-based, after-vaccination health checker for people who receive COVID-19 vaccines called V-safe. V-safe uses text messaging and web surveys from CDC to check in with vaccine recipients following COVID-19 vaccination. V-safe also provides second vaccine dose reminders if needed, and telephone follow-up to anyone who reports medically significant adverse events.

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Learn more about COVID-19 vaccine safety from the CDC