Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
UPDATE
Given new evidence on the B.1.617.2 (Delta) variant, CDC has updated the guidance for fully vaccinated people. CDC recommends universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. Children should return to full-time in-person learning in the fall with layered prevention strategies in place.
UPDATE
The White House announced that vaccines will be required for international travelers coming into the United States, with an effective date of November 8, 2021. For purposes of entry into the United States, vaccines accepted will include FDA approved or authorized and WHO Emergency Use Listing vaccines. More information is available here.
UPDATE
Travel requirements to enter the United States are changing, starting November 8, 2021. More information is available here.

Selected Adverse Events Reported after COVID-19 Vaccination

Selected Adverse Events Reported after COVID-19 Vaccination
Safety of COVID-19 Vaccines

Some people have no side effects. Many people have reported side effects that are generally mild to moderate and go away within a few days.

What You Need to Know

  • COVID-19 vaccines are safe and effective.
  • CDC recommends everyone ages 5 years and older get vaccinated as soon as possible to protect against COVID-19 and its potentially severe complications. CDC has updated its recommendation for COVID-19 vaccines with a preference for mRNA vaccines (Pfizer-BioNTech and Moderna).
  • Millions of people in the United States have received COVID-19 vaccines under the most intense safety monitoring program in U.S. history.
  • CDC, the U.S. Food and Drug Administration (FDA), and other federal agencies continue to monitor the safety of COVID-19 vaccines.
  • Adverse events described on this page have been reported to the Vaccine Adverse Event Reporting System (VAERS)external icon.
  • VAERS accepts reports of any adverse event following vaccination.

Serious adverse events after COVID-19 vaccination are rare but may occur.

CDC is providing timely updates on the following serious adverse events of interest:

  • Anaphylaxis after COVID-19 vaccination is rare and has occurred in approximately 5 people per one million vaccinated in the United StatesAnaphylaxis, a severe type of allergic reaction, can occur after any kind of vaccination. If it happens, healthcare providers can effectively and immediately treat the reaction. Learn more about COVID-19 vaccines and allergic reactions, including anaphylaxis.
  • Thrombosis with thrombocytopenia syndrome (TTS) after Johnson & Johnson’s Janssen (J&J/Janssen) COVID-19 vaccination is rare. TTS is a rare but serious adverse event that causes blood clots in large blood vessels and low platelets (blood cells that help form clots). As of January 6, 2022, more than 17.7 million doses of the J&J/Janssen COVID-19 vaccine have been given in the United States. CDC and FDA identified 57 confirmed reports of people who got the J&J/Janssen COVID-19 vaccine and later developed TTS.

    CDC has also identified nine deaths that have been caused by or were directly attributed to TTS following J&J/Janssen COVID-19 vaccination. Women ages 30-49 years, especially, should be aware of the increased risk of this rare adverse event. There are other COVID-19 vaccine options available for which this risk has not been seen.
    • To date, three confirmed cases of TTS following mRNA COVID-19 vaccination (Moderna) have been reported to VAERS after more than 496 million doses of mRNA COVID-19 vaccines administered in the United States. Based on available data, there is not an increased risk for TTS after mRNA COVID-19 vaccination.
  • Guillain-Barré Syndrome (GBS) in people who have received the J&J/Janssen COVID-19 vaccine is rare. GBS is a rare disorder where the body’s immune system damages nerve cells, causing muscle weakness and sometimes paralysis. Most people fully recover from GBS, but some have permanent nerve damage. After more than 17.7 million J&J/Janssen COVID-19 vaccine doses administered, there have been around 294 preliminary reports of GBS identified in VAERS as of January 6, 2022. These cases have largely been reported about 2 weeks after vaccination and mostly in men, many in those ages 50 years and older.

    Based on the data, the rate of GBS within the first 21 days following J&J/Janssen COVID-19 vaccination was found to be 21 times higher than after Pfizer-BioNTech or Moderna (mRNA COVID-19 vaccines). After the first 42 days, the rate of GBS was 11 times higher following J&J/Janssen COVID-19 vaccination. Analysis found no increased risk of GBS after Pfizer-BioNTech or Moderna (mRNA COVID-19 vaccines). CDC and FDA will continue to monitor for and evaluate reports of GBS occurring after COVID-19 vaccination and will share more information as it becomes available.
  • Myocarditis and pericarditis after COVID-19 vaccination are rare. Myocarditis is inflammation of the heart muscle, and pericarditis is inflammation of the outer lining of the heart. Most patients with myocarditis or pericarditis after COVID-19 vaccination responded well to medicine and rest and felt better quickly.  As of January 6, 2022, VAERS has received 2,077 preliminary reports of myocarditis or pericarditis among people ages 30 years and younger who received COVID-19 vaccines.

    Most cases have been reported after receiving Pfizer-BioNTech or Moderna, (mRNA COVID-19 vaccines) particularly in male adolescents and young adults. Through follow-up, including medical record reviews, CDC and FDA have verified 1,175 reports of myocarditis or Learn more about myocarditis and pericarditis, including clinical considerations, after mRNA COVID-19 vaccination.
  • Reports of death after COVID-19 vaccination are rare. FDA requires healthcare providers to report any death after COVID-19 vaccination to VAERS, even if it’s unclear whether the vaccine was the cause. Reports of adverse events to VAERS following vaccination, including deaths, do not necessarily mean that a vaccine caused a health problem. More than 520 million doses of COVID-19 vaccines were administered in the United States from December 14, 2020, through January 10, 2022. During this time, VAERS received 11,225 reports of death (0.0022%) among people who received a COVID-19 vaccine. CDC and FDA clinicians review reports of death to VAERS including death certificates, autopsy, and medical records.

    A review of reports indicates a causal relationship between the J&J/Janssen COVID-19 vaccine and TTS. CDC scientists have conducted detailed reviews of TTS cases and made the information available to healthcare providers and the public:


    Continued monitoring has identified nine deaths causally associated with J&J/Janssen COVID-19 vaccination. CDC and FDA continue to review reports of death following COVID-19 vaccination and update information as it becomes available.