Different COVID-19 Vaccines
and Vaccine Safety
Authorized COVID-19 Vaccines
Currently, two vaccines are authorized and recommended to prevent COVID-19:
Pfizer-BioNTech COVID-19 vaccine
- Recommended for people aged 16 years and older.
- 2 shots given 21 days apart.
- Based on
evidence from clinical trials, the Pfizer-BioNTech vaccine was 95% effective at preventing laboratory-confirmed COVID-19 illness in people without evidence of previous infection.
Moderna's COVID-19 vaccine
- Recommended for people aged 18 years and older.
2 shots given 28 days apart.
evidence from clinical trials, the Moderna vaccine was 94.1% effective at preventing laboratory-confirmed COVID-19 illness in people who received two doses who had no evidence of being previously infected.
Vaccines in Phase 3 Clinical Trials
Phase 3 clinical trials are in progress or being planned for three additional COVID-19 vaccines in the United States:
- AstraZeneca's COVID-19 vaccine
- Janssen's COVID-19 vaccine
- Novavax's COVID-19 vaccine
Side effects usually start within a day or two of getting the vaccine. They should go away in a few days. The most common side effects include:
At injection site:
The U.S. Food and Drug Administration (FDA) has granted Emergency Use Authorizations (EUA) for two COVID-19 vaccines which have been shown to be safe and effective.
Emergency Use Authorizations
Vaccine Safety Monitoring
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.
Learn more about COVID-19 vaccine safety from the CDC.