What Is Myocarditis? Heart Inflammation in Some Pfizer Vaccine Patients Probed in Israel

Israel's health ministry has said it is investigating a small number of cases of myocarditis—heart inflammation—in people who have received the Pfizer COVID vaccine.

It is not yet clear whether the number of myocarditis cases is higher than would be expected in the general population, or whether the cases are connected to the vaccine, according to Nachman Ash, Israel's pandemic response coordinator.

Ash added: "The Health Ministry is currently examining whether there is an excess in morbidity (disease rate) and whether it can be attributed to the vaccines," Reuters reported on Sunday.

Ash said there had been "tens of incidents" out of over 5 million people who have been fully vaccinated in the country. The total population is just over 9 million.

According to a leaked health ministry report, there had been 62 recorded cases of myocarditis in vaccine patients, The Times of Israel reported, citing Israeli TV news outlet Channel 12. Most cases had allegedly developed after the second shot and most were present in men under 30.

Pfizer told Reuters it was aware of the investigations and added: "Adverse events are regularly and thoroughly reviewed and we have not observed a higher rate of myocarditis than what would be expected in the general population. A causal link to the vaccine has not been established."

Myocarditis is an inflammation of the heart which is usually caused by a viral infection—though there are many potential causes. Some things that can cause the condition include the Epstein-Barr virus and sexually transmitted infections such as Hepatitis C, Herpes, and Chlamydia.

A number of bacteria can also lead to myocarditis, as can certain parasites and fungal infections.

The condition may also be caused by a reaction to a drug or other substance, or another condition that causes inflammation.

Often, myocarditis has no symptoms and people can recover without even knowing they had it. When symptoms do arise, they may include shortness of breath, chest pain, an abnormal heartbeat, fatigue, and other signs of infection such as fever, sore throat, or headache.

The condition may affect the heart's electrical system and reduce its ability to pump blood. In severe cases, it means the body doesn't get enough blood, which in turn can lead to clots, stroke, or heart attack.

People are advised to go and see their doctor if they have symptoms of myocarditis, particularly chest pain and shortness of breath. Patients should call for emergency medical help if severe symptoms are present, according to the Mayo Clinic.

The health group adds that getting vaccinated against infections may help prevent myocarditis. It also advises regular hand-washing and avoiding people who have viral illnesses.

Israel medics
Medical workers vaccinate people against COVID at the Tel Aviv Sourasky Medical Center, December 20, 2020 in Tel Aviv, Israel. More than 5 million have now been fully vaccinated in the country. Amir Levy/Getty