A small number of people vaccinated against the coronavirus disease 2019 (Covid-19) have developed a rare heart condition, according to the Centers for Disease Control and Prevention (CDC), but researchers say the risks of contracting the coronavirus are a greater threat to health than the complication.

About 1,200 people, most of whom are age 30 or younger, have reported experiencing symptoms of heart inflammation following receipt of one of the two-dose COVID-19 vaccines, the CDC reported Tuesday.

This is out of approximately 296 million doses of the vaccines from Pfizer-BioNTech and Moderna distributed nationally through June 11, 52 million of which were given to children and adults age 12 to 30, the agency said.

Of the 1,226 cases of heart inflammation, or myocarditis, reported after vaccination, 1,194 involved recipients age 12 to 30, the data showed.

Still, “the benefits of Covid-19 vaccination to individual persons and at the population level clearly outweighed the risks of myocarditis after vaccination,” the agency researchers wrote.

Myocarditis, a condition in which the heart becomes inflamed, causing an irregular heartbeat and shortness of breath, has been reported with the Pfizer-BioNTech and Moderna vaccines since both received U.S. Food and Drug Administration approval in December, according to the CDC.

Most cases of the side effect, which can cause serious health problems, have been reported in younger males, the agency said.

The vaccines, both of which require two doses for maximum effectiveness, are made using similar technology and are designed to mimic the genetic make-up of the coronavirus in order to prepare the immune system to respond to it.

Myocarditis has also been reported in people with severe cases of Covid-19, including in young children infected.

However, for every 1 million second doses of the two-dose vaccines administered to males age 12 to 29, 11,000 Covid-19 cases, 560 hospitalizations, 138 ICU admissions and six deaths due to the virus could be prevented, the agency said.

In comparison, there will be an estimated 39 to 47 cases of myocarditis following vaccination in this age group, CDC said.

“CDC has updated patient education and communication materials reflecting this information for the Pfizer-BioNTech and Moderna Covid-19 vaccines,” the agency researchers wrote.

“These are important to ensure that vaccine recipients, especially males aged 12 to 29 years, are aware of increased risk for myocarditis and to seek care if they develop symptoms of myocarditis,” they said.