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Different COVID-19 Vaccines
and Vaccine Safety

Authorized COVID-19 Vaccines

Currently, three vaccines are authorized and recommended to prevent COVID-19:

  • Comirnaty/Pfizer-BioNTech COVID-19 vaccine
    • On August 23, 2021, FDA granted full approval for Pfizer-BioNTech (COMIRNATY) COVID-19 Vaccine for individuals 16 years of age and older.
    • Recommended for people aged 5 years and older (The vaccine continues to be available under emergency use authorization (EUA) for individuals 5 through 15 years of age).
    • 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 COVID-19 vaccine
    • Recommended for people aged 18 years and older.
    • 2 shots given 28 days apart.
    • Based on 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.
  • Johnson & Johnson (Janssen) vaccine
    • Recommended for people aged 18 years and older.
    • 1 shot given.
    • On April 23, 2021, the Pennsylvania Department of Health notified all COVID-19 vaccine providers that the pause in administering doses of the Johnson & Johnson (Janssen) vaccine has been lifted. The move follows updated guidance announced today by the Centers for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA).

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
  • Novavax's COVID-19 vaccine

Side Effects

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:

  • Pain
  • Swelling
  • Redness

Throughout body:

  • Chills
  • Tiredness
  • Headache

Vaccine Safety

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.

Date updated: 11/3/2021