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A Project of The Annenberg Public Policy Center
SciCheck’s COVID-19/Vaccination Project

How safe are the vaccines?


This article is available in both English and Español

No serious safety concerns were found in the clinical trials of the vaccines that have been authorized for use in the United States. 

On April 13, the CDC and Food and Drug Administration recommended “a pause in the use” of the Johnson & Johnson vaccine. The agencies lifted the pause on April 23, shortly after the CDC’s Advisory Committee on Immunization Practices voted 10-4 to resume the vaccine’s use with a warning about a rare, severe type of blood clot and low blood platelets that mostly occurred in women aged 18 to 49 years old. At its April 23 meeting, the ACIP reported that, as of April 21, there were 15 cases of the rare clotting condition combined with low levels of platelets among women, including three deaths, out of nearly 8 million vaccinations.

Since the rollout of the Pfizer/BioNTech and Moderna vaccines in December 2020, a small number of people in the U.S. have had serious allergic reactions following receipt of the shots. 

Some allergic reactions, including a potentially life-threatening reaction known as anaphylaxis, are to be expected with any vaccine. Fortunately, that kind of severe reaction is typically very rare, occurs within minutes of inoculation and can be treated. 

As of Jan. 18, there have been 2.5 cases of anaphylaxis per million doses of the Moderna vaccine and 4.7 cases per million of the Pfizer/BioNTech vaccine, according to a report by the Centers for Disease Control and Prevention. Those who develop anaphylaxis are usually given epinephrine, the drug found in EpiPens. None of these reactions has led to death. On Feb. 26, Johnson & Johnson said it had received a report of one anaphylactic reaction in South Africa.

To make sure serious allergic reactions can be identified and treated, all people receiving a vaccine should be observed for 15 minutes after getting a shot, and anyone who has experienced anaphylaxis or had any kind of immediate allergic reaction to any vaccine or injection in the past should be monitored for a half hour. People who have had a serious allergic reaction to a previous dose or one of the vaccine ingredients should not be immunized. Also, those who shouldn’t receive one type of COVID-19 vaccine should be monitored for 30 minutes after receiving a different type of vaccine.