In a recent study published in Journal of the Canadian Medical Association, researchers observed the incidence of myocarditis after messenger ribonucleic acid (mRNA)-based vaccination against coronavirus disease 2019 (COVID-19). In addition, they compared estimates with predicted incidences based on historical incidences assessed before COVID-19 vaccination was rolled out in British Columbia (BC), Canada.
study: Observed and expected rates of myocarditis after SARS-CoV-2 vaccination: a population-based cohort studyImage Credit: Lightspring/Shutterstock
As of September 2022, approximately 4.5 million people in British Columbia were receiving vaccines to prevent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, some people are hesitant to get the vaccine, mainly because of fear of side effects. Prelicensing studies did not suggest a risk of myocarditis after vaccination. However, post-marketing studies have associated myocarditis with SARS-CoV-2 mRNA vaccines, particularly post-vaccination adverse events, raising safety concerns, especially in younger age groups.
Evidence from case reports and case series suggests a higher rate of myocarditis in young adults following mRNA-1273 compared to the BNT162b2 vaccine. Unfortunately, data on the incidence of myocarditis after the third vaccination are lacking. This is important for future booster strategies against COVID-19.
In this study, researchers received mRNA SARS-CoV-2 vaccination (BNT162b2 or mRNA-1273) according to the BC Immunization Registry between December 15, 2020 and March 10, 2022. We recruited individuals over 12 years old.
The BC Immunization Registry is a surveillance platform that collects population health care data, including COVID-19-related lab tests, vaccinations, case surveillance, hospitals and intensive care units. [ICU] admission. It also maintains records of emergency department (ED) visits, physician claims, drug dispensing, laboratory tests, chronic illnesses, and deaths dating back to 2008.
The team used BC COVID-19 cohort data on hospital admissions and ED visits from 2015 to 2020 to estimate the background (expected) rate of myocarditis incidence. It compares the number of cases reported to the number of cases expected under the null hypothesis. The null hypothesis means that there is no association between intervention and disease.
Observed rates of myocarditis-related hospitalizations or emergency department visits after SARS-CoV-2 mRNA vaccination were higher than expected rates. In addition, the researchers noted that men aged 18-29 years (the younger population) had the highest incidence of myocarditis after the second vaccination. Although the overall rate of myocarditis per 100,000 doses was very low with both mRNA vaccines, the rate was approximately four times higher with the mRNA-1273 vaccine than with the BNT162b2 vaccine. Incidence of inflammation decreased after the third vaccination. Additionally, most cases were mild, had short hospital stays, and recovered quickly. Overall, the study results showed the overall safety of mRNA vaccines.
The researchers noted the highest absolute rate of myocarditis in men aged 12-17 years who received the BNT162b2 vaccine. The observed-to-expected ratio of myocarditis in these men was also the highest. The mRNA-1273 vaccine was not administered to the 12- to 17-year-old age group. Also, no previous studies reported this comparison. They combined age groups (e.g., 16–29 years or 12–39 years) or analyzed proportions of only BNT162b2 recipients aged 12–17 years. Current study analysis suggested a higher risk of myocarditis after his mRNA-1273 than his BNT162b2 vaccine in younger individuals, although additional research is needed for the 12- to 17-year-old age group. Is required.
There is increasing evidence of a potential causal link between the SARS-CoV-2 mRNA vaccine and myocarditis. However, the risk-benefit assessment appears to be biased towards the benefits of mRNA SARS-CoV-2 vaccines. A recent US analysis found that one million seconds of administration of the mRNA SARS-CoV-2 vaccine resulted in 560 hospitalizations, 138 his ICU admissions, 11,000 cases, and 6 his COVID-19 Related deaths were saved. myocarditis; Similarly, the study by Patone et al. found 10 additional myocarditis events per million patients 28 days after receiving his second dose of the mRNA-1273 vaccine. On the contrary, after testing positive for SARS-CoV-2, in the same time frame he had 40 additional myocarditis events in 1 million patients.
The researchers observed a higher-than-expected incidence of myocarditis after mRNA vaccination, although absolute rates remained low. SARS-CoV-2 vaccination reduced the severity of infection, hospitalizations, and deaths. Indeed, the benefits of mRNA COVID-19 vaccination outweigh the risk of developing myocarditis. Young people aged 18 to her 29 were most affected by myocarditis. Therefore, the preferred strategy should be continuous vaccination, albeit with adverse event surveillance.
- Observed and expected rates of myocarditis after SARS-CoV-2 vaccination: a population-based cohort study, Zaeema Naveed, Julia Li, Michelle Spencer, James Wilton, Monika Naus, Héctor Alexander Velásquez García, Michael Otterstatter, Naveed Zafar Janjua , CMAJ 2022 Doi: https://doi.org/10.1503/cmaj.220676, https://www.cmaj.ca/content/194/45/E1529