Risk for myocarditis, pericarditis may depend on which mRNA vaccine is used

The two competing COVID-19 mRNA vaccines appear to be associated with different risk levels for the development of myocarditis or pericarditis. This is according to a study in JAMA Open Network designed to determine the rates of reported myocarditis or pericarditis following mRNA vaccination by product, age, sex, dose number and interdose interval. The population-based cohort study was conducted using data for Ontario from December 2020 to September 2021. All individuals who had at least one COVID-19 mRNA vaccination in that time were included. Read: Half-hour online training session helps teenagers deal with academic-related stress: study During the period of interest, 19,740,741 doses of mRNA vaccines were administered in Ontario. Among these were a total of 417 cases of myocarditis or pericarditis reported after immunization, and out of this only 297 (71.2%) met the Brighton Collaboration definitions for myocarditis and pericarditis. Most, 207 (69.7%) occurred following a second dose of COVID-19 mRNA vaccine, and 228 (76.8%) were in males. As for the type of event, 107 (36.0%) of the cases were myopericarditis, followed by 105 (35.4%) cases of myocarditis, and 85 (28.6%) with pericarditis. Nearly all the events 290 (97.6%) involved an emergency department visit. Most, 210 (70.7%), were admitted to hospital, with 87 being hospitalized for myocarditis, 33 for pericarditis, and 90 for myopericarditis. Details pertaining to symptom onset were available for 295 (99.3%) of the cases, and researchers found that the median time to onset was three days after vaccination. Most occurred within a week. There were more events after the second dose of an mRNA vaccine than after the first dose, particularly in people who received mRNA-1273 (Moderna) as the second dose. The highest rate of myocarditis or pericarditis was seen in males aged 18 to 24 years following mRNA-1273 as the second dose (299.5 cases per 1,000,000 doses) compared to BNT162b2 as the second dose (59.2 cases per 1 000 000 doses in this age group, the study said. The second highest rate was seen in males aged 12 to 17 years after their second dose of BNT162b2 (97.3 cases per 1,000,000 doses). The authors noted that guidance from several international immunization advisory suggest longer intervals between vaccine doses to help improve the durability of the immune response and that this might also reduce the rare risk of myocarditis or pericarditis. Read: Ontario hospitals warn of more upcoming ER closures through the summer

Risk for myocarditis, pericarditis may depend on which mRNA vaccine is used

Register for free access or login.

Related Topics