The Department of Health today said it received from the Hospital Authority a total of three reports of suspected myocarditis for adolescents who have received BioNTech vaccines up to July 19 and their conditions were stable.

In response to media enquiries, the department noted around 63,000 doses of BioNTech vaccines have been administered to adolescents aged 12 to 15 in the same period.

The three cases involved one 12-year-old and two 15-year-old boys. They complained of chest pain about two days after receiving the second dose of BioNTech vaccine.

They were all admitted to the authority's hospitals for monitoring and treatment, and their conditions were stable.

These cases will be passed to the Expert Committee on Clinical Events Assessment Following COVID-19 Immunization for causality assessment.

The expert committee noted that there were reports from overseas drug regulatory authorities about cases of myocarditis and pericarditis following vaccination, especially among younger vaccine recipients.

The committee has endorsed the inclusion of myocarditis and pericarditis in the list of serious or unexpected adverse events following immunisation to enhance monitoring.

The department has also been closely monitoring adverse events of myocarditis or pericarditis among adolescents of 12 to 15 years old.

According to the BioNTech vaccine manufacturer, cases of myocarditis and pericarditis have primarily occurred within 14 days following vaccination, more often after the second vaccination and in younger men.

The supplier has also updated the product's package insert to include myocarditis and pericarditis as its adverse reactions.

The department reminded adolescents and young adults to avoid strenuous exercise for one week after vaccination.

They should seek immediate medical attention if they develop symptoms indicative of myocarditis or pericarditis such as acute and persisting chest pain, shortness of breath or palpitations following vaccination.