Hundreds of millions of doses of COVID-19 vaccines have now been administered in the U.S. and only a few, very rare, safety concerns have emerged. The vast majority of people experience only minor, temporary side effects such as pain at the injection site, fatigue, headache, or muscle pain — or no side effects at all. As the Centers for Disease Control and Prevention has said, these vaccines “have undergone and will continue to undergo the most intensive safety monitoring in U.S. history.”
A small number of severe allergic reactions known as anaphylaxis, which are expected with any vaccine, have occurred with the authorized and approved COVID-19 vaccines. Fortunately, these reactions are rare, typically occur within minutes of inoculation and can be treated. Approximately 2 to 5 per million people vaccinated have experienced anaphylaxis after a COVID-19 vaccine, according to the CDC.
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.
The Johnson & Johnson vaccine has been linked to an increased risk of rare blood clots combined with low levels of blood platelets, primarily in women ages 18 to 49. Early symptoms of the condition, which is known as thrombosis with thrombocytopenia syndrome, or TTS, can appear as late as three weeks after vaccination and include severe or persistent headaches or blurred vision, leg swelling, and easy bruising or tiny blood spots under the skin outside of the injection site.
As of Dec. 8, the syndrome has been confirmed in 57 cases, including nine deaths, after more than 16.9 million doses of the J&J vaccine. Although TTS remains rare, because of the availability of mRNA vaccines, which are not associated with this serious side effect, the CDC began recommending the Pfizer/BioNTech and Moderna shots over J&J’s on Dec. 16.
On July 13, the FDA added warnings to fact sheets on the J&J vaccine about an observed increased risk of Guillain-Barré Syndrome, a disorder in which the immune system attacks nerve cells. Most people who develop GBS fully recover, although some have permanent nerve damage and the condition can be fatal.
As of Dec. 8, there have been about 278 preliminary reports of GBS. Most cases have occurred around two weeks post-vaccination and in males, primarily those 50 years of age and older.
There is emerging evidence that the Pfizer/BioNTech and Moderna mRNA vaccines may very rarely cause inflammation of the heart muscle (myocarditis) or of the surrounding lining (pericarditis), particularly in male adolescents and young adults.
As of Dec. 8, the agency says there have been 1,908 preliminary reports of either condition in people 12 through 29 years of age following immunization with any COVID-19 vaccine. The bulk of the reports, which are through the Vaccine Adverse Event Reporting System and do not necessarily mean the vaccine caused the problem, are with the Pfizer and Moderna vaccines and are more common among males and after the second dose. “Through follow-up, including medical record reviews, CDC and FDA have confirmed 1,106 reports of myocarditis or pericarditis,” the CDC says.
Health officials have emphasized that the potential vaccine-related myocarditis and pericarditis cases are rare and the benefits of vaccination still outweigh the risks. Early evidence suggests these myocarditis cases are less severe than typical ones. The CDC has also noted that most patients who were treated “responded well to medicine and rest and quickly felt better.”
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