Heart failure and even death have occurred among people who received a COVID-19 vaccine, according to a new study.
Six people across the four Nordic countries died from myocarditis, a form of heart inflammation, within 90 days of hospital admission after being vaccinated with a messenger RNA (mRNA) vaccine, researchers reported. Twenty-two vaccinated people were diagnosed with heart failure within 90 days of hospital admission with myocarditis.
Myocarditis is caused by the mRNA COVID-19 vaccines made by Pfizer and Moderna, experts in the United States and elsewhere have said. Death is a known outcome. Many people diagnosed with the condition are hospitalized.
Many of those heart failure or death diagnoses happened in those 40 and older. Eight occurred among 12- to 39-year-olds.
The researchers also found that 62 people who experienced heart inflammation following vaccination were readmitted to a hospital within 90 days of discharge. Of the readmissions, 41 percent were among the younger age group.
ComparisonMore people experienced myocarditis after COVID-19 vaccination than after COVID-19 infection—530 versus 109—according to the new paper.
Researchers took those numbers, and figures representing myocarditis cases prior to the pandemic. They then looked at what percentage led to heart failure or death and calculated the risk for each category.
Myocarditis after COVID-19 vaccination was less likely to lead to a diagnosis of heart failure or death when compared to the historical myocarditis cases, the study estimated. On the other hand, myocarditis after a COVID-19 infection was more likely to lead to heart failure or death.
The risk of readmission to a hospital was lower for people with heart inflammation after COVID-19 vaccination or COVID-19 infection. Among certain groups, though, such as vaccinated women, the risk was about the same as it was for those with conventional myocarditis.
"Taken together, our findings suggested that the outcomes of myocarditis after vaccination were less severe than other types of myocarditis during the first 90 days after the onset of myocarditis," Anders Husby, a Danish epidemiologist, and the other researchers said.
Despite the death and heart failure cases among the vaccinated, the researchers said their results were "reassuring" and "should be considered when weighing the benefits and potential risks of mRNA vaccines against the SARS-CoV-2 virus at the individual and population levels." SARS-CoV-2 causes COVID-19.
Limitations of the paper include not having access to cardiac magnetic resonance imaging or other evaluation data that would give insight into the severity of each myocarditis case.
Pfizer and Moderna didn't respond to requests for comment.
The post-COVID-19-infection heart injury "reflects patients with bad hearts getting very ill," Koka said. On the other hand, post-COVID-19-vaccination myocarditis often strikes young, healthy males without a disposition to heart injury.
Dr. Tracy Høeg, a California epidemiologist, said she disagreed with the conclusions of the study's authors.
Update From CDCThe U.S. Centers for Disease Control and Prevention (CDC) identified a higher-than-expected rate of myocarditis in many age groups, particularly among males, in 2021.
The reports were lodged between December 2020 and August 2021.
Studies on the reporting rates to VAERS have estimated that the rate of post-vaccination problems is underreported to the system and the researchers largely agreed, pointing to how most reports of myocarditis after COVID-19 vaccination had been verified.
"Therefore, the actual rates of myocarditis per million doses of vaccine are likely higher than estimated," they said.
A significant portion, or 46 percent, also suffered from depression, and others suffered from pain and trouble performing usual activities, according to the surveys.
On Feb. 3, Ian Kracalik, a CDC researcher and the lead author of that paper, presented an update of the surveys to the National Vaccine Advisory Committee.
In a new round of surveys collected at least one-year post-myocarditis, 23 percent of 60 patients who responded said they were experiencing chest pain, and others still struggle with symptoms such as fatigue and heart palpitations.
The percentage of patients reporting at least one symptom, 33 percent, was down from 68 percent in the previous round of surveys.
"We're seeing a reduction in the number of patients we're seeing reporting at least one symptom," Kracalik said.
Still, 41 percent of the patients said they have depression, and another 32 percent reported experiencing pain.
Health care providers who completed a separate set of surveys 5 to 13 months after the myocarditis reported no patient deaths but that 14 percent of the patients, primarily young males, weren't cleared for all physical activity and that four had the same status or had worsened since the last surveys, including one who was readmitted to a hospital.
Abnormal findings were reported for multiple patients from cardiac MRIs and other measures, such as electrocardiograms.
Limitations of the ongoing study include there being no standard of care for myocarditis after mRNA vaccination.
Problem With New VaccinesBecause they aren't as effective against newer variants, the original Moderna and Pfizer vaccines were updated in 2022 to target some of the new strains in addition to the Wuhan variant. The updated shots were introduced as boosters, only available for people who received a primary series.
Officials still need to investigate more to determine a link but have described the new shots as being similar to the original vaccines.