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 6,637 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, have published corresponding numbers from the same data base for myocarditis associated with the same vaccine in males and females aged 12-15.
Their research covers 404,407 people 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 and 8.09 cases per 100,000 after a second dose.
For females, the estimates were 0 cases per 100,000 after a first dose and 0.69 cases per 100,000 after a second dose.
“The pattern observed, mainly following the second vaccination in males, suggests causality,” the group wrote.
Leveraging passive surveillance reports
Another new report adds a twist to updated numbers from the U.S. Vaccine Adverse Event Reporting System (VAERS).
Prevalences derived from the passive-surveillance data base, known for including case records of inconsistent quality or completeness, are considered especially prone to reporting bias, the authors acknowledged.
The current analysis, however, plunges deep into VAERS-reported cases of presumed SARS-CoV-2 vaccine-associated myocarditis to help clarify “more of the characteristics of the patients and some of the treatments and short-term outcomes,” Matthew E. Oster, MD, MPH, said in an interview.
Dr. Oster, from the Centers for Disease Control and Prevention and Emory University, Atlanta, is lead author on the study’s Jan. 25, 2022, publication in JAMA.
The group reviewed charts and interviewed involved clinicians to adjudicate and document presentations, therapies, and the clinical course of cases reported as SARS-CoV-2 vaccine–associated myocarditis from December 2020 to August 2021. Out of the nearly 2000 reports, which were limited to patients younger than 30, the group identified 1,626 likely cases of such myocarditis arising within 7 days of a second mRNA vaccine dose.
The confirmed cases consistently represented higher prevalences than expected compared with prepandemic myocarditis claims data for both sexes and across age groups spanning 12-29 years.
For example, rates were highest for adolescent males – about 106 and 71 cases per million second doses of the Pfizer-BioNTech vaccine in those aged 16-17 and 12-16, respectively, for example. They were lowest for women aged 25-29, at 2.23 cases per million second Pfizer-BioNTech doses; the highest rate among females was about 11 per million for the 16-17 age group.
The observed rates, Dr. Oster said, represent an update to VAERS numbers published June 2021 in Morbidity and Mortality Weekly Report covering cases through June 2021.
“Overall, the general risk of having myocarditis from the vaccines is still extremely low. Even in the highest risk groups, it is still extremely low, and still lower than the risk of having cardiac complications from COVID,” he noted.