By Dr Rohit Khurana
Our clinic has recently seen a number of healthy patients, mostly teenagers and young men, who started to describe symptoms such as chest discomfort, laboured breathing and palpitations (the sense that their heartbeat is abnormal) several days after administration of the 1st or 2nd dose of the Pfizer/BioNTech and the Moderna mRNA–based lipid nanoparticle vaccines. Naturally, the media reports of complications have evoked a fear of developing pericarditis and myocarditis. The inevitable question of safety to have the 2nd dose is a concern for the individual if the symptoms have occurred after the 1st dose.
Myocarditis is inflammation of the muscle of the heart, and pericarditis is inflammation of the tissue that forms a sac around the heart. The diagnosis of myocarditis is made based on the history, supported by electrocardiogram (ECG) changes, elevations in the level of the cardiac biomarker, troponin and impaired contractility of the heart muscle seen on an echocardiogram or typical changes, as defined by expert consensus guidelines, obtained on magnetic resonance imaging (MRI) of the heart. The specific mechanisms by which immunologic responses to mRNA-based COVID-19 vaccines could lead to myocarditis are not established.
In reality, the evidence would suggest that this complication is extremely rare and has been reported after the 2nd dose has been administered. Estimating the true incidence is problematic from the hundreds of millions of doses of the vaccine that have been administered. The most comprehensive data about the risk of myocarditis following immunization with mRNA vaccines comes from Israel. The Israeli Ministry of Health recently posted data describing 121 myocarditis cases occurring within 30 days of a second dose of mRNA vaccine among 5 049 424 persons, suggesting a crude incidence rate of approximately 24 cases per million following a second dose in this subset of their vaccinated population. Updated information is accessible at: https://www.gov.il/en/departments/news/01062021-03
Vaccinated individuals can usually return to their normal daily activities after their symptoms improve. They should speak with their doctor about return to exercise or sports. Our current advice is to avoid strenuous exercises within one week of vaccination, keep rested and well-hydrated. Unless symptoms persist and in which case, it’s important to seek medical advice, the 2nd dose is important to achieve the maximal immunity benefits.
Secondly, it’s important to appreciate the perspective of potential vaccine-associated myocarditis within the context of the current pandemic. Infection with SARS-CoV-2 is a clear cause of serious cardiac injury in many patients. The mechanism of injury may be direct infection, an immune-mediated response, or a combination of direct or indirect effects. Given that COVID-19 vaccines are remarkably effective at preventing infection, any risk of rare adverse events following immunization must be carefully weighed against the very substantial benefit of vaccination.