Heart inflammation after Covid-19 jabs: What does it mean for you?

Vials with Pfizer-BioNTech and Moderna coronavirus vaccine labels are seen in an illustration photo.
Vials with Pfizer-BioNTech and Moderna coronavirus vaccine labels are seen in an illustration photo.PHOTO: REUTERS

SINGAPORE - Rare cases of heart inflammation have been reported with Covid-19 vaccines that use mRNA technology - namely the Pfizer-BioNTech and Moderna jabs, both overseas and locally. The Straits Times finds out the answers to some questions.

Q: What is it?

A: Myocarditis is caused by the inflammation of the heart muscle while pericarditis is the inflammation of the outer lining of the heart.

It is often caused by a viral infection but can also be the result of certain chemicals or allergic reactions to medications, autoimmune diseases and other kinds of infections, including by bacteria and parasites.

Myocarditis and pericarditis are not heart attacks, which are usually caused by blockages in the blood vessels that supply the heart.

Q: Are these conditions common?

A: The exact prevalence in Singapore is not known.

This is because the severity of symptoms varies substantially - some people have no symptoms while others may have only mild symptoms - and so it is often not detected. In most cases, the inflammation is mild, but it can be severe enough to require hospitalisation and even cause death.

Singapore's Health Sciences Authority (HSA) said in an update that as at June 30, in general, five to seven individuals per 100,000 people a year are hospitalised for myocarditis or pericarditis. This makes up roughly 280 to 400 cases a year.

Q: Is there a link between heart inflammation and the mRNA vaccine?

A: These cases in adolescents and young adults are "likely linked" to the mRNA vaccines, a group of doctors advising the United States Centres for Disease Control and Prevention said on June 23.

People generally recover from the symptoms and do well.

Inflammation of the heart was also reported in some Covid-19 patients last year, most likely the result of an overactive immune system giving rise to the inflammation. As mRNA vaccines lead to a similar, but milder, immune response, this could also result in inflammation.

Q: How many people suffer from heart inflammation after getting the mRNA vaccines?

A: As at June 30, HSA has received 12 reports of myocarditis and pericarditis after close to 5.5 million doses of vaccines administered. Five of the cases occurred in adults aged 30 and above, two of whom were women.

Seven of the cases involved males aged below 30.

Six of the cases occurred after the first dose, said HSA. Most were reported to have occurred within a week of the individual receiving the vaccine.

HSA also noted that a greater frequency of heart attacks and strokes was not observed in vaccinated people here.

In the US, more than 1,200 cases of heart inflammation have been reported as at June 2021 and most were mild cases. It is estimated that there are just 12.6 heart inflammation cases per million second doses administered.

Q: How do I know if I have myocarditis?

A: The typical symptoms are chest pain, shortness of breath and a rapid pulse.

Symptoms may also be non-specific, ranging from tiredness, muscle aches and a mild fever. The patient may also feel shortness of breath occurring more readily than before, wrote Dr Mak Koon-Hou, a cardiologist at Gleneagles Medical Centre, in his 2015 book Understanding And Preventing Sudden Death.

Q: What happens after myocarditis?

A: Generally, most patients respond well to treatment and recover.

The patient is usually treated symptomatically and closely monitored for abnormal heart rhythms and heart failure. Physical exertion is believed to increase the risk of sudden death, Dr Mak wrote.

When a person exercises, the demand on the heart increases. If the heart muscle is already inflamed, strenuous physical activity may worsen the amount of damage to the heart muscle, adversely affecting its function.

Sporting activities should be avoided until the condition is completely resolved and medical treatment should be given prior to resumption of exercise.