A recent observational study conducted by United States-based scientists has revealed that the incidence rate of myocarditis due to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is about 450 per million cases among young males. Young males with the coronavirus disease 2019 (COVID-19), which is the disease that results from infection by SARS-CoV-2, are 6-times more susceptible to myocarditis than those who received the COVID-19 vaccine. The study is currently available on the medRxiv* preprint server.
Background
A growing amount of evidence has identified myocarditis as a rare side-effect of mRNA-based COVID-19 vaccines. The risk-benefit analysis of COVID-19 vaccines has indicated that young males under the age of 30 years are 10-times more susceptible to myocarditis as compared to those over the age of 30. The highest risk of myocarditis has been observed in males aged 12 to 17 years after receiving the 2nd vaccine dose.
Besides vaccination, SARS-CoV-2 infection has been found to increase the risk of myocarditis. In hospitalized COVID-19 patients, myocarditis has been identified as a serious complication, even for those without a history of cardiovascular disease. However, there remains an insufficient amount of information available to assess the risk of myocarditis in low-risk COVID-19 patients.
Study design
In the current study, the scientists have estimated the prevalence of myocarditis in young male COVID-19 patients who are under the age of 20 years. The study was conducted on young males and females with confirmed COVID-19 diagnoses who did not have a history of any cardiovascular disease.
Specifically, three age groups were considered, which included individuals between 12 and 17 years of age, 12-15 years, and 16-19 years. The studied age groups corresponded to the previously identified high-risk myocarditis cohorts related to mRNA-based COVID-19 vaccination.
To include information about any missed COVID-19 cases, an adjusted number of COVID-19 cases was derived for each tested age group using the population-level infection rate and study-estimated COVID-19 prevalence.
An incidence of myocarditis that occurred within 90 days following COVID-19 diagnosis was considered for the analysis. Patients immunized with mRNA-based COVID-19 vaccines prior to a myocarditis diagnosis were excluded from the analysis.
Important observations
In the 12-17 years age group, about 0.09% of male COVID-19 patients were diagnosed with myocarditis. This corresponded to a rate of 876 myocarditis cases per million male COVID-19 patients. After adjusting for missed COVID-19 cases, an incidence rate of 450 myocarditis cases per million patients was estimated.
Similarly, for the 12-15 and 16-19 age groups, the adjusted myocarditis cases per million patients were estimated to be 601 and 561, respectively.
In female COVID-19 patients belonging to the age groups of 12-17 years, 12-15 years, and 16-19, the adjusted rates of myocarditis per million patients were estimated to be 213, 235, and 708, respectively.
By considering the entire study population, including males and females, the adjusted rates of myocarditis per million patients were estimated to be 328, 416, and 643 for the 12-17 years, 12-15 years, and 16-19 years age groups, respectively.
Of all identified myocarditis cases, about 40% occurred within 5 days and 60% occurred within 19 to 82 days following COVID-19 diagnosis.
Study significance
According to the study estimates, the prevalence of myocarditis in young male COVID-19 patients is 450 per million cases. Previous studies have estimated that the incidence rate of myocarditis following mRNA vaccination in the high-risk age group of 12-17 years is about 76 cases per million vaccine recipients.
Based on this information, the study highlights that young males with SARS-CoV-2 infection are 6-times more susceptible to develop myocarditis as compared to those who received mRNA-based COVID-19 vaccines.
*Important notice
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.
