To date, the systems in place to monitor the safety of these vaccines have found four serious types of adverse events following COVID-19 vaccination, with evidence that suggests an increased risk after certain types of COVID-19 vaccinations were administered. They are:
Anaphylaxis is a severe type of allergic reaction with symptoms such as hives, difficulty breathing, low blood pressure, or significant swelling of the tongue or lips. Anaphylaxis can occur after any kind of vaccination. Anaphylaxis after COVID-19 vaccination is rare and has occurred in approximately two to five people per million persons vaccinated in the United States. If anaphylaxis happens, healthcare providers can immediately, and effectively, treat the reaction. Learn more about COVID-19 vaccines and allergic reactions, including anaphylaxis.
Thrombosis with Thrombocytopenia Syndrome (TTS)
Thrombosis occurs when blood clots block blood vessels. Thrombocytopenia is a condition in which a low blood platelet level interferes with the formation of blood clots.
As of November 24, 2021, more than 16.4 million doses of the Johnson & Johnson/Janssen COVID-19 vaccine have been given in the United States. CDC and FDA identified 54 confirmed reports of people who got the Johnson & Johnson/Janssen COVID-19 vaccine and later developed TTS. TTS after Johnson & Johnson/Janssen COVID-19 vaccination is rare.
Women ages 50 and younger especially should be aware of the rare but increased risk of this adverse event associated with the Johnson & Johnson/Janssen vaccine. There are other COVID-19 vaccine options available. Learn more about Johnson & Johnson/Janssen COVID-19 vaccine and TTS.
Myocarditis and Pericarditis
Myocarditis is an inflammation of the heart muscle. Pericarditis is inflammation of the area around the heart. Myocarditis and pericarditis after COVID-19 vaccination are rare. As of November 24, 2021, VAERS has received 1,949 reports of myocarditis or pericarditis out of the tens of millions of people ages 30 and younger who received mRNA COVID-19 vaccines.
Most cases of myocarditis and pericarditis have been reported after mRNA COVID-19 vaccination (Pfizer-BioNTech or Moderna), particularly in male adolescents and young adults. Through follow-up, including medical record reviews, CDC and FDA have confirmed 1,071 reports of myocarditis or pericarditis.
CDC and its partners are investigating these reports to assess whether there is a relationship to COVID-19 vaccination. A recent study published in the New England Journal of Medicine found that the estimated incidence of myocarditis among people who had received at least one dose of mRNA COVID-19 vaccine was approximately 2.13 cases per 100,000 persons. Most of these cases were reported to be mild or moderate in severity. Learn more about COVID-19 vaccines and myocarditis and pericarditis.
Guillain-Barré Syndrome (GBS)
GBS is a rare, autoimmune disorder in which a person’s own immune system damages the nerves, causing muscle weakness and sometimes paralysis. GBS occurs rarely, usually following a viral infection. CDC and FDA are monitoring reports of Guillain-Barré Syndrome (GBS) in people who have received the Johnson & Johnson/Janssen COVID-19 vaccine.
Most people fully recover from GBS, but some have permanent nerve damage. After more than 16.4 million Johnson & Johnson/Janssen COVID-19 vaccine doses administered, approximately 268 preliminary reports of GBS have been identified in VAERS as of November 24, 2021. These cases have largely been reported about two weeks after vaccination and mostly in men, ages 50 years and older.
CDC will continue to monitor and evaluate reports of GBS occurring after COVID-19 vaccination and will share more information as it becomes available.
Reports of Death Are Rare
More than 459 million doses of COVID-19 vaccines were administered in the United States from December 14, 2020, through November 29, 2021. During this time period, VAERS received 10,128 reports of death (0.0022%) among people who received a COVID-19 vaccine.
FDA requires healthcare providers to report any death after COVID-19 vaccination to VAERS, even if it is unclear that the vaccine was the cause. Reports to VAERS of health problems or deaths following vaccination do not necessarily mean that a vaccine caused a health problem. Reports to VAERS provide information on possible concerns, and allow scientists to look more closely at VAERS and other health data to figure out whether the problem was related to vaccination. CDC clinicians review reports of death to VAERS—including death certificates, autopsy, and medical records.