Feb. 22 (UPI) — Teens and young adults are less likely to develop a heart-related complication associated with COVID-19 after being vaccinated than they would be if they caught the virus, according to a study published Tuesday by the Lancet Child and Adolescent Health.
In the United States, 21 confirmed cases of the complication, called multi-system inflammatory syndrome, or MIS-C, were reported among more than 21 million people ages 12 to 20 years after they received a dose of a COVID-19 vaccine, the data showed.
This amounts to one case of MIS-C per 1 million people vaccinated in this age group, the researchers said.
However, of the 21 cases of MIS-C, 15 had been infected with the virus, while the remaining six may have developed it as a side effect after vaccination, according to the researchers.
These six cases of post-vaccination MIS-C equates to a rate of 0.3 per 1 million vaccinated, they said.
All of the people who developed the complication after vaccination had been given the Pfizer-BioNTech shot, the only one authorized for use in children in the United States at the time the study was conducted, the researchers said.
“As part the comprehensive effort to monitor COVID-19 vaccine safety in the United States, [the Centers for Disease Control and Prevention} has been closely monitoring cases of MIS-C in vaccinated children,” study co-author Dr. Anna R. Yousaf said in a press release.
“Our results suggest that MIS-C cases following COVID-19 vaccination are rare, and that the likelihood of developing MIS-C is much greater in children who are unvaccinated and get COVID-19,” said Yousaf, an epidemic intelligence service officer with the CDC.
The agency recommends COVID-19 vaccination for everyone age 5 years and older in the United States.
MIS-C is a new illness identified during the COVID-19 pandemic that affects children about four to six weeks after infection. It has some of the same symptoms as Kawasaki disease, a disorder that causes inflammation of the blood vessels, according to the American Heart Association.
However, MIS-C causes more severe inflammation that can affect different parts of the body, including the heart, lungs, kidneys and digestive tract, it notes.
A study published last summer by JAMA Network Open estimated that for every 1 million people age 21 years and younger infected with COVID-19, 224 develop MIS-C.
About 80% of children who become sick enough from the virus to require hospital care suffer from the complication, which can cause the heart to lose some of its ability to pump properly, coronary artery dilation and leaking heart valves, based on earlier studies.
Most recover within three to five months, research suggests.
Symptoms include fever, rash, eye redness and gastrointestinal symptoms, such as diarrhea, stomach ache and nausea, according to the CDC.
Nearly 7,000 MIS-C cases have been reported during the pandemic, with 59 deaths, as of Jan. 31, the agency said.
Although more than one-third of all children diagnosed with COVID-19 were infected with the Omicron variant, which emerged in late November, a corresponding uptick in MISC-C cases has not occurred, based on CDC data.
The researchers on this study emphasized they are unable to determine if vaccination contributed to the MIS-C illness in the 21 cases, meaning it is unclear whether it was a side effect associated with the shot.
It is possible that some of the identified cases had other unrecognized inflammatory conditions that coincidentally occurred after vaccination, they said.
Of those affected, 11 received one dose and 10 received two doses of the vaccine before MIS-C illness onset, the researchers said.
All 21 cases in the analysis were hospitalized, with 12 admitted to an intensive care unit, and all were eventually discharged home, according to the researchers.
“As with COVID-19 illness, clinicians and researchers are still learning about MIS-C,” Yousaf said.
“Our investigation highlights the challenges in diagnosing MIS-C, the importance of considering alternative diagnoses, and the need to monitor for MIS-C illness,” she said.