Certain jabs can cause immune cells to attack the body, leading to myocarditis and pericarditis, particularly in young men, scientists say
Certain Covid-19 vaccines can trigger immune responses that may inflame heart tissue and lead to potentially fatal complications in rare cases, with young men being especially susceptible, according to a new study.
The paper, authored by Stanford University researchers and published in the Science Translational Medicine journal, examined why some patients developed myocarditis or pericarditis after receiving mRNA jabs such as those produced by Pfizer and Moderna.
Researchers found that immune cells can, in some cases, recognize the foreign RNA delivered by the vaccines and mount a strong response. In rare instances, this response has led to the release of large amounts of cytokines – immune-signaling proteins that can damage heart cells.
Vaccine-associated myocarditis has occurred in about one in 140,000 people after a first dose and around one in 32,000 after a second dose, according to figures cited by The Telegraph, with incidence peaking among males aged 30 or younger.
Symptoms have included chest pain, shortness of breath, fever and palpitations, typically appearing within days of vaccination. Most patients have recovered quickly, although hospitalization and deaths have been reported in rare cases.
The findings come as the US Food and Drug Administration reportedly intends to place a “black box” warning, the agency’s most serious safety label, on Covid-19 vaccines, according to CNN. The warning would alert consumers to risks such as myocarditis and pericarditis, although the plan has not been finalized.
Covid-19 vaccines were developed and authorized rapidly after the World Health Organization declared a coronavirus pandemic in March 2020 and were later mandated in many countries. The rollout proved controversial, with critics claiming the jabs were poorly tested and that side effects posed greater risks than the virus itself.
However, scientists and regulators have maintained that Covid-19 infection carries a greater overall risk of serious illness and long-term complications than vaccination, and have stressed that the benefits of immunization outweigh the short-term risks of rare heart-related side effects.
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