“We used laboratory test results of troponin levels to further eliminate unlikely cases of carditis,” Wong said. The health records were linked to a “population-based vaccination record” maintained by the government’s department of health.
About 10 control patients from among all hospitalized patients without carditis were matched by age, sex, and admission date to each of the 160 carditis cases. About 83% of cases and 92% of the controls were unvaccinated.
Among those who received the Pfizer-BioNTech vaccine, representing 12.5% of cases and 4.2% of controls, the estimated carditis incidence was 0.57 per 100,000 doses. For those who received CoronaVac, representing 4.4% of cases and 3.9% of controls, it was 0.31 per 100,000 doses.
In adjusted analysis, the odds ratio (OR; 95% confidence interval [CI]) for carditis among Pfizer-BioNTech vaccine recipients, compared with unvaccinated controls, was:
- 3.57 (CI, 1.93 – 6.60) overall
- 4.68 (CI, 2.25 – 9.71) for males
- 2.22 (CI, 0.57 – 8.69) for females
- 2.41 (CI, 1.18 – 4.90) for ages 18 and older
- 13.8 (CI, 2.86 – 110.4) for ages 12-17
Myocarditis accounted for most of the excess cases, with an overall OR of 9.29 (CI, 3.94 – 21.9). The OR reached only 1.06 (CI, 0.35 – 3.22) for pericarditis alone.
The case-control study is noteworthy for its design, which contrasts with the many recent case series and passive or active surveillance studies, and even the more robust population-based studies of vaccine-related myocarditis, observed Dongngan Truong, MD, University of Utah and Primary Children’s Hospital, Salt Lake City, who wasn’t part of the study.
Among its strengths, she told theheart.org | Medscape Cardiology, are its linkage of comprehensive hospital and vaccination data sets for two different vaccines; and that it corroborates other research suggesting there is “something in particular about mRNA vaccination that seems to be associated with the development of myocarditis.”
Active Surveillance in Israel
In an October 2021 report based on an Israeli Ministry of Health database covering up to May 2021, rates of myocarditis arising within 21 days of a second Pfizer-BioNTech dose in 16- to 19-year-olds reached about 1 per 6637 males and 1 per 99,853 females. Those numbers compared with 1 per 26,000 males and 1 per 218,000 females across all age groups.
Now authors led by Dror Mevorach, MD, Hadassah Medical Center, Jerusalem, Israel, have published corresponding numbers from the same data base for myocarditis associated with the same vaccine in males and females aged 12 to 15.
Their research correspondence published online January 26 in the New England Journal of Medicine covers 404,407 in that age group who received a first dose of the mRNA-based vaccine and 326,463 who received the second dose from June to October, 2021. Only 18 cases of myocarditis were observed within 21 days of either dose.
The estimated rates for males were:
- 0.56 cases per 100,000 after a first dose
- 8.09 cases per 100,000 after a second dose
For females, the estimates were:
- 0 cases per 100,000 after a first dose
- 0.69 cases per 100,000 after a second dose
“The pattern observed, mainly following the second vaccination in males, suggests causality,” the group writes in a supplement published with their letter.