Up to one in 7,000 American teens developed heart inflammation after their Covid vaccine

Thousands of American teens may have had heart infections after getting a Covid shot, a study suggests.

Researchers found that up to one in 7,000 boys ages 12 to 15 developed myocarditis after receiving the Pfizer vaccine.

The condition — which is mild for most but can cause a recurrent palpitation in rare cases — was most common after the second dose.

Covid is also mild for most teens: Only 1,745 Americans under 18 die from the disease, compared to more than 800,000 over 50s.

Experts said their paper was not proof that people should stop vaccinating, and that the benefits still “far outweigh” the risks.

Covid itself is known to cause myocarditis, and in some studies it is known to be more common in infections than after inoculation.

Vaccinating children has been hugely controversial during the pandemic because of the smaller risks Covid poses to them compared to older adults.

The chart above shows the risk of myocarditis per dose, based on people under the age of 40 and up to seven days after getting their shot. The risk was highest after the second dose

Researchers at health care provider Kaiser Permanente assessed 340 cases of myocarditis and pericarditis in hospitals in eight US states.

Myocarditis is when the heart muscle becomes inflamed while pericarditis is when the inside of the heart becomes inflamed.

Overall, in all individuals under 40 years of age, the frequency of the adverse reaction was one in 30,000 after a second dose.

It was one in 200,000 after a first shot and one in 50,000 after a booster dose.

Experts haven’t tried to explain the difference between doses, though it may be related to the immune system getting a stronger response to the second shot.

Myocarditis is triggered when the body’s immune system causes inflammation – often because it is fighting an infection such as Covid.

The findings are published today in the Annals of Internal Medicine.

For the paper, they checked 6.9 million recipients of the Covid vaccine whether they visited an ER department with myocarditis.

This included symptoms such as a fluttering heart or shortness of breath within a week of vaccination.

All participants received their shot between December 14, 2020 and May 31, 2022, in eight US states, including California, Colorado and Georgia.

A total of 119 cases of myocarditis were confirmed out of the 3.4 million people who received their second dose in the study.

For those who got their first shot, there were 18 cases from 3.5 million patients.

And of the 1.8 million participants who received the booster dose, 77 later came to the hospital with myocarditis.

Cases were included if they were detected within seven days of vaccination and could be independently verified by investigators.

Children or teenage boys ages 12 to 15 were most likely to develop myocarditis after a second dose.

On the other hand, women aged 18 to 29 rarely experienced the side effect.

The study did not look at rates between Pfizer and Moderna vaccines, although Moderna recipients are believed to have a slightly higher risk.

It also did not include a control group, a population that was monitored for myocarditis after not receiving a Covid vaccine.

dr. Kristin Goddard, of Kaiser Permanente who led the study and others, said the numbers don’t show people should stop getting Covid vaccines.

‘Our findings may provide a risk-benefit analysis, which has consistently shown so far that the benefits of mRNA vaccination far outweigh the risks.

“Continued communication with patients and healthcare providers about the risk of myocarditis and pericarditis after Covid vaccination … is warranted.”

The data came from the Vaccine Safety Datalink System, which involves hospitals and emergency departments in eight states.

Some cautioned that the numbers may mean underreporting, as some patients don’t notice they have myocarditis or pericarditis.

The Centers for Disease Control and Prevention (CDC) say that myocarditis is reported rarely, but most likely in adolescents and young men.

Analysis conducted for the agency and published in April this year found that after the second dose, the rates rose to one in 600 for boys ages 12 to 15.

But it was much less common in women aged 18 to 29, with very few cases identified.

This analysis did not include boosters.


Myocarditis is a rare condition.  It is usually caused by an infection reaching the heart

Myocarditis is a rare condition. It is usually caused by an infection reaching the heart

Myocarditis is heart inflammation caused by a viral infection, such as COVID-19.

In severe cases, the inflammation can weaken the heart, cause an abnormal heartbeat, or even lead to death.

Symptoms usually include chest pain or shortness of breath.

Patients can treat the condition with medication aimed at regulating the heart rate and improving heart function. In some rare cases, patients have had to have a device implanted in their heart to regulate the heartbeat.

Myocarditis is a mild, temporary condition in the vast majority of cases, experts say.

Heart inflammation is uncommon in professional athletes who have had mild COVID-19 infection, and most do not need to be sidelined, according to a 2021 study conducted by major professional sports leagues.

This image shows a normal heart muscle compared to an inflamed heart muscle

This image shows a normal heart muscle compared to an inflamed heart muscle

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