In April, reports of myocarditis being diagnosed in the few days following receipt of Comirnaty vaccine, particularly following the second dose, started to appear in countries using this vaccine in younger adults from 16 years (Israel and USA). The vast majority of the cases of myocarditis reported to US CDC (to the end of May) following Comirinaty vaccination have been discharged from hospital (95%) with most fully recovered (81%). CDC is currently reviewing data from the Vaccine Safety Datalink network, which is able to directly compare rates of various conditions occurring with and without receipt of Comirinaty vaccine in large numbers of people, to evaluate the relative incidence and gather information about severity of myocarditis in vaccinated and unvaccinated young adults.
Myocarditis and pericarditis are uncommon conditions, usually thought to be related to viral infection leading to inflammation of the heart muscle or the tissue surrounding the heart. Chest pain is the most common symptom. Diagnosis is based on elevated levels of cardiac enzymes in blood tests, and by electrocardiogram and echocardiogram tests. Rates of incidence vary between populations and by gender and age; for example, the incidence in adolescent males aged 14 to 18 years is significantly higher than in females.
MedSafe is closely monitoring for any reports of myocarditis following COVID-19 vaccination in New Zealand. For further information please refer to the WHO’s statement.