Higher risk of myocarditis after SARS-CoV-2 infection than after COVID-19 vaccination

Risk of hospitalization or death myocarditis Results from self-administered case series studies have reported higher increases after SARS-CoV-2 infection than COVID-19 vaccination.

Although the risk of myocarditis from infection remained after vaccination, findings suggest that it was significantly reduced, suggesting a protective benefit from the cardiovascular effects of SARS-CoV-2 infection. is being added.

However, in contrast to these findings, the risk of myocarditis observed 1–28 days after the second dose of mRNA-1273 vaccine was similar to the risk post-infection, especially in young men. did.

“Although the net benefit of vaccination at the individual or population level should not be limited to the risk of myocarditis, quantifying this risk is critical to the potential for severe illness, especially with SARS-CoV. It is important for young people with low sex.

Hippisley-Cox et al previously reported an association between the first and second doses of COVID-19 vaccine and myocarditis, and an increased risk of hospitalization or death from myocarditis with both adenoviral (ChAdOx1) and mRNA vaccines. reported.

The team noted that their findings also determined that the risk of myocarditis after vaccination was small compared to the risk after a positive SARS-CoV-2 test. Due to its prevalence in individuals under 12 months and males, additional analyzes stratified by age and sex are preferred.

They also highlighted the observation that the risk of myocarditis was higher after the second vaccination than the first, making it urgent to assess the risk of booster vaccination. patients and applied to patients who received a COVID-19 vaccination or booster to assess the association between infection and myocarditis risk stratified by age and sex.

The researchers estimated the rate ratio and excess number of hospitalizations or deaths from myocarditis per million people 1–28 days after continuous administration of the COVID-19 vaccine or after a positive SARS-CoV-2 test. did.

There were 42,842,345 individuals who received at least one dose of ChAdOx1 (n = 20,650,685), BNT162b2 (n = 20,979,704), or mRNA-1273 (n = 1,211,956) between December 2020 and December 2021 Did. Of this population, a total of 21,242,629 received his third vaccination.

In addition, data show that among those who received at least one dose of vaccine, 5,934,153 (13.9%) were positive for SARS-CoV-2, including 2,958,026 (49.8%) before the first vaccination. I’m here.

The researchers observed that 2681 patients (0.007%) were hospitalized or died of myocarditis during the study period. They noted that a total of 617 (0.001%) of these events occurred between 1 and 28 days after vaccination.

The data suggest that the risk of myocarditis was increased from 1 to 28 days after the first dose of ChAdOx1 (incidence ratio [IRR]1.33; 95% CI, 1.09–1.62) and first, second, and booster doses of BNT162b2 (IRR, 1.52) [95% CI, 1.24 – 1.85]; 1.57 [95%  CI,  1.28–1.92]and 1.72 [95%  CI,  1.33–2.22]Respectively).

However, these observations were found to be lower than the risk after a positive SARS-CoV-2 test before and after vaccination (IRR, 11.14 [95% CI, 8.64 – 14.36] and 5.97 [95% CI, 4.54 – 7.87]Respectively).

Furthermore, this association was noted to be stronger in men <40 years of age for all vaccines. The number of excess myocarditis events per million was higher after her second dose of mRNA-1273 than with a positive SARS-CoV-2 test (97 [95% CI, 91 –99] versus 16 [95% CI, 12 – 18]). Women experienced a similar increased risk of myocarditis after a second dose of mRNA-1273.

Hippisley-Cox noted that a comparison of mortality from myocarditis among persons infected with or vaccinated with SARS-CoV-2 was not possible because the analysis included only vaccinated persons. pointed out.

“Therefore, COVID-19 patients who died of myocarditis before receiving vaccination would not be included, and mortality from myocarditis after SARS-CoV-2 would be underestimated,” added Hippisley-Cox. .

the study, “Risk of myocarditis after sequential administration of COVID-19 vaccine and SARS-CoV-2 infection by age and sexwas published in circulation.