A study by the Oregon Health Authority found reassuring evidence that a complication of the COVID-19 vaccine — myocarditis — was not associated with cardiac deaths among previously healthy young people, in the 19 months following the initial vaccine rollout.
However, due to its limitations, the study could not rule out the possibility that in very rare cases, cardiac death may be a complication of the vaccine.
The study was published this week in the Centers for Disease Control and Prevention’s public health bulletin Morbidity and Mortality Weekly Report.
Myocarditis, which is essentially inflammation of the heart muscle, is a known but rare complication of the COVID-19 vaccine. It happens most often to adolescents and young males within seven days after the second dose of an mRNA COVID-19 shot.
The OHA study looked at deaths in Oregon that occurred following the initial rollout of the COVID-19 vaccine, from June 1, 2021, to Dec. 31, 2022.
The authors used the Oregon death certificate database to look for people aged 16-30 years old who died of cardiac causes or of undetermined causes during that time.
They found a total of 1,292 deaths among people in that age range. Of those, none had COVID-19 vaccination listed as a cause of death on their death certificate.
The authors then narrowed their focus to 66 males and 35 females whose deaths were due to cardiac events or unknown causes, according to their death certificates.
The researchers used the state’s vaccination records to see whether any of those young people had died within 100 days of receiving a mRNA COVID-19 vaccine dose. They found three deaths that met that criteria.
One male died 21 days after COVID-19 vaccination. His cause of death was listed as congestive heart failure attributed to hypertension and other chronic conditions. A second male died 45 days after vaccination, of an “undetermined natural cause.” One female died of undetermined causes four days after COVID-19 vaccination. Her death certificate listed chronic respiratory failure as a factor.
Lars Grosse-Wortmann, a pediatric cardiologist at Oregon Health & Science University and an expert on COVID-19 vaccine myocarditis, was not involved in the study.
He said that combining big datasets, as the study did, is a helpful approach to better understand a rare vaccine complication like myocarditis.
“To me, the study is reassuring in the way that they didn’t find a big smoking gun,” Grosse-Wortmann said. “They didn’t all of a sudden identify a dozen patients where it had that close chronological association with their vaccine.”
“On the other hand, it’s neither big enough nor detailed enough for me to say, ‘This study leads me to think there’s no risk for sudden cardiac death,’” he added.
Without detailed medical records for the three patients the study identified who died within 100 days of vaccination, it was hard to draw firm conclusions in those cases.
In particular, the death of the female could plausibly have been vaccine-related, given the timeline in that case, Grosse-Wortmann said.
“I would say we don’t know,” he said. “The conclusion from the paper is correct, the data does not support the association, but it does not lay the question to rest whether sudden cardiac death could occur.”
Grosse-Wortmann, at the Federal Drug Administration’s request, has been leading an effort to compile research and better characterize myocarditis following mRNA vaccination.
That effort has found the prognosis of young patients with myocarditis related to the mRNA COVID-19 vaccine is generally positive. People with myocarditis after vaccination typically have mild cases of it, and they tend to recover quickly.
However, Grosse-Wortmann said, some show signs of heart injury and scarring in imaging scans that seem somewhat at odds with the mild clinical presentation of their cases.
Because the first cases were reported in 2021, the longest any patient has been followed is three years.
“That’s long enough to say these patients do clinically well, but probably too short to say if the scars that some of them carry in their hearts have any significance for their long term health and survival,” Grosse-Wortmann said.
Any risk due to a rare vaccine side-effect, Grosse-Wortmann said, has to be weighed against the benefits of vaccination. In the case of the COVID-19 shots, the potential benefits include protection against death, long ICU and hospital stays, long COVID, and the long-term cardiovascular risk factors of a COVID-19 infection.
The OHA study authors also looked at COVID-19 deaths among adolescents and young people during the same time period in 2021 and 2022. COVID-19 was cited as the cause of death for 30 Oregon residents in that age group. Almost all were unvaccinated.
“It is clear that the risk, if any, of cardiac death linked to COVID-19 vaccination is very low, while the risk of dying from COVID-19 is real,” said Paul Cieslak, co-author of the study. “We continue to recommend COVID-19 vaccination for all persons 6 months of age and older.”
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