Myocarditis post-vaccination; should we be concerned?
By Maryanne Demasi, PhD
Israel was the canary in the coal mine, the first country to signal a concerning spike in cases of myocarditis (inflamed heart muscle).
Early data suggested myocarditis was occurring more commonly in younger men (16-19 years), particular after the second dose, at a rate of 1 in 6600.
The US CDC tried to douse the flames. According to its monitoring system, myocarditis rates after vaccination had not differed from expected baseline rates.
The following month, the CDC published its own data – in males under 40, myocarditis occurred a rate of 1 in 31,000 after two doses of an mRNA vaccine.
The problem was not going away. By July 2021, the EU had conducted its own investigation and concluded there was a “potential link between heart inflammation and mRNA vaccines.”
To counter public fear, authorities reassured their citizens that the cases were mild, incredibly rare, and resolved without treatment. Hence, the benefits of inoculating young people, outweighed the risks.
The studies roll in
By September 2021, a pre-print study by Høeg and associates, sounded the alarm again.
The authors took a more granular look at the US Vaccine Adverse Event Reporting System (VAERS) and provided a more sensitive analysis than the CDC.
The incidence of myocarditis in young males was 1 in 10,600 (16–17yr) and 1 in 6,200 (12-15yr), and the majority, 86% of them, required some form of hospital care.
But then, the FDA released a report which may have humbled the critics.
The report contained Pfizer’s own data showing higher rates of myocarditis than previously reported by the CDC, 1 in 15000 (16–17yr males).
Moderna appeared to be linked to more cases than Pfizer.
So, out of an abundance of caution, Sweden, Norway, and Finland broke ranks with their European counterparts and suspended the use of Moderna’s vaccine in everyone under 30.
France and Germany soon followed.*
Authorities continued to push for mass vaccination, saying that young people were more likely to develop myocarditis if they caught COVID-19 – citing a poorly validated publication that used “estimates”.
The studies continued to pour in.
One from Hong Kong which showed the incidence of myocarditis in males 12-17yrs after two doses of Pfizer was 1 in 2700, and another by Oxford researchers, which sparked a frenzied discussion among academics.
It was the first study that strongly challenged the mainstream narrative that myocarditis was more common after COVID-19 than after vaccination in young males under 40 (graph).
This was true following the 2nd and 3rd Pfizer jab and the 1st and 2nd Moderna jab – but the effect inverted in older age groups.
Finally, a pre-print study from Kaiser Permanente also found high rates of myopericarditis after two doses of an mRNA vaccine; 1 in 1800 in males aged 18-24y and 1 in 2600 in males aged 12-17y.
The authors concluded that “the true incidence of myopericarditis is markedly higher than the incidence reported to US advisory committees.”
Is myocarditis post-vaccination ‘mild’?
Dr Peter McCullough is a Texas-based cardiologist, internist, epidemiologist and co-editor of the journal, Reviews in Cardiovascular Medicine.
Throughout the pandemic, Dr McCullough has been managing the cardiovascular complications of both the viral infection and the injuries developing after the COVID-19 vaccine.
He rejects the notion that most cases of post-vaccination myocarditis are trivial or “mild”.
“They suddenly develop chest pain, elevated troponin levels [indicates muscle heart damage], EKG changes and about three quarters have evidence of heart damage by echocardiography or MRI,” he said.
Dr McCullough’s experience at the bedside is supported by a large case series of suspected post-vaccine myocarditis in people under 21y, published in Circulation.
Cardiac MRIs showed 77% had abnormalities, and of them, 99% had late gadolinium enhancement (signifies fibrosis or scar tissue) and 72% had myocardial oedema (swelling of heart muscle).
It is too early to tell what the long-term impacts will be for those who develop myocarditis post-vaccination, but a 2019 study published in Circulation suggested 13% of myocarditis cases end up with impaired heart function.
Dr McCullough says this could be just the tip of the iceberg.
“I think there are large numbers of sub-clinical myocarditis going on. Perhaps one of the manifestations of this is that we're seeing more and more athletes, mostly in that age group 18-24yrs [mandated to take the vaccine], collapsing on the soccer field,” says Dr McCullough.
“One of the things they have to do for treatment is absolutely abstain from any physical activity because extreme exercise while the heart is inflamed will trigger sudden cardiac death.”
Social media platforms have been flooded with video montages of soccer players collapsing on the field, but sceptics have denied any link to the vaccines, saying that sudden cardiac death has always been a problem in sport and that the increased events are a ‘coincidence’.
Recently, health authorities in New Zealand said that a 26-year-old man had died from myocarditis linked to the Pfizer vaccine.
Background rate of paediatric myocarditis?
Myocarditis is normally very rare in the paediatric population (4 per million per year), but the surge in post-vaccination cases reported to the CDC VAERS (n=23,317 cases as of December 31, 2021) is concerning to Dr McCullough.
“If the background rate is 4 per million per year, we now have vaccine-induced myocarditis rates that are around 200 to 400 per million in a year [1 in 5000-2500],” says Dr McCullough
“And don’t forget, that’s not boosted children. Once they start getting boosted, the numbers could run up to 600 to 800 per million per year [1 in 1600 – 1250],” he adds
The rates of myocarditis are more common in young males, probably due to androgens (hormones like testosterone).
Brazilian researchers have claimed to achieve favourable outcomes after treating COVID-19 patients with anti-androgen therapy, but more research is needed.
It may also explain why some data suggest that pre-pubescent 5–11-year-olds may be less affected by myocarditis than those over 12.
What is the biological mechanism?
The mechanism of vaccine-induced myocarditis is not definitively known but it is likely to be related to the lipid nanoparticles in the vaccine which carry the mRNA.
The vaccine is designed to be injected intramuscularly (deltoid) and produce a local immune reaction. However, surrogate studies in regulatory data show that lipid nanoparticles can deposit in tissues beyond the site of injection to the liver, adrenal glands, spleen and ovaries.
“Lipid nanoparticles get distributed throughout the body, and invariably, some are taken up in the heart. The mosaic of cells with the lipid nanoparticles can start to produce the spike protein which incites inflammation in those tissues,” explains Dr McCullough.
“We also now know that spike protein circulates in the bloodstream for about two weeks after the shot, and in some people, it can circulate and be measurable up to a month after the shot. That free circulating spike protein can also be deposited into the heart.”
A study by Avolio and colleagues demonstrates that spike protein has the capacity to cause molecular and functional changes in human vascular pericytes, which are the support cells around the capillaries surrounding the heart muscle cells.
Interpretation of findings
There are several things to consider when deciding to vaccinate children and young adults against COVID-19.
1. Many young people (40% of children in the US) have already been exposed to COVID-19 and therefore have recent immunity.
2. The survival rate of COVID-19 for children and adolescents is >99.99%, according to a study by Stanford Professor John Ioannidis, therefore, the risk of death is low.
3. The risk of hospitalisation for young people without co-morbidities is also low, e.g. at the peak of the delta outbreak in Sydney, the majority of infected children (<16y) had asymptomatic or mild disease, hospitalisation was uncommon, and more children were hospitalised for social reasons, than for medical reasons.
4. Now that omicron has surfaced and presents as a milder disease (30-50% less risk of hospitalisation than delta), the current stable of vaccines are significantly less efficacious against the new variant, they do not prevent infection, nor do they prevent transmission.
5. Now that the US has recommended everyone over 12 should receive a booster shot, what will be the incremental risk that comes with each mRNA injection? The European Union regulator has now warned that frequent COVID-19 booster shots could adversely affect the immune system.
Summarising the evidence, some experts now suggest that the benefits of an mRNA vaccine in young adults whose risk is already low, does not outweigh the harms.
Others have called for a more nuanced approach to vaccinating kids against COVID-19, ranging from spacing the two doses further apart, recommending only one dose or only vaccinating children at high risk of COVID-19 complications.
Unfortunately, the uncertainty and the lack of transparency from authoritative sources has likely damaged public confidence in routine vaccinations for generations to come.
*Pfizer is still used in these countries. Moderna may show higher rates of myocarditis because it has a higher concentration of mRNA (100µg) compared to Pfizer (30µg).
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