What is the clinical evidence from this study?

Study design: Observational. Population: Healthy high school students receiving COVID-19 vaccination (n=4928). Intervention: BNT162b2 vaccine vs. Pre-vaccine baseline. Primary outcome: Incidence of significant arrhythmias and myocarditis.

October 28, 2022Open Access

Changes of ECG parameters after BNT162b2 vaccine in the senior high school students

SCShuenn‐Nan ChiuNational Taiwan University Hospital YCYih‐Sharng ChenNational Taiwan University Hospital CHChia-Chen HsuTaipei Tzu Chi Hospital

Key Result

Cardiac symptoms were common after the second dose of the BNT162b2 vaccine in high school students, but the combined incidence of significant arrhythmias and myocarditis was only 0.1%.

Study Design

Type

Observational (n=4,928)

Multicenter

Yes

Structured PICO

Does serial ECG screening effectively detect cardiac adverse effects after the second dose of the BNT162b2 vaccine in high school students?

Population

4,928 high school students (mean age 16.7 years, 7.1% female) underwent serial ECG screening before and 2 days after their second dose of the BNT162b2 vaccine.

Exposure

Second dose of BNT162b2 vaccine with serial 12-lead ECG screening (performed 1-10 days before and 2 days after vaccination).

Comparator

Baseline (pre-vaccine) ECGs and symptoms (self-controlled comparison).

Outcome

Changes in ECG parameters (QRS duration and QT interval) and incidence of cardiac adverse effects (myocarditis and significant arrhythmia).safety

Serial ECG screening demonstrates that while self-reported cardiac symptoms are common after the second dose of the BNT162b2 vaccine in adolescents, the actual incidence of myocarditis and significant arrhythmias is extremely low.

Limitations

Enrolled students from only four schools, limiting statistical power.
Low vaccination rate in the study population due to low COVID-19 incidence and fear of adverse effects.
Not all patients who received the second dose completed the study.
Pre-vaccine ECG was obtained after the first vaccine dose, which may mitigate the observed influence of the vaccine.
ECGs were performed 2 days after vaccination, which could decrease the detection rate of cardiac adverse effects that peak at 3-4 days.
Relied on the school reporting system for serious cardiac outcomes, and not all students received a complete cardiology workup.
18 patients with ECG changes did not seek medical investigation after a positive screening result.
Findings may not apply to students with severe underlying diseases who did not receive the vaccine at school.

Abstract

Abstract Purpose: To determine the ECG parameters change and the efficacy of ECG screening for cardiac adverse effect after the second dose of BNT162b2 vaccine in young population. Methods: In December 2021, in cooperation with the school vaccination system of Taipei City government, we performed a ECG screening study during the second dose of BNT162b2 vaccines. Serial comparisons of ECGs and questionnaires survey were performed before and after vaccine in four male-predominant senior high schools. Results: Among 7934 eligible students, 4928 (62.1%) were included in the study. The male/female ratio was 4576/352. In total, 763 students (17.1%) had at least one cardiac symptom after the second vaccine dose, mostly chest pain and palpitations. The depolarization and repolarization parameters (QRS duration and QT interval) decreased significantly after the vaccine with increasing heart rate. Abnormal ECGs were obtained in 51 (1.0%) of the students, of which 1 was diagnosed with mild myocarditis and another 4 were judged to have significant arrhythmia. None of the patients needed to be admitted to hospital and all of these symptoms improved spontaneously. Using these five students as a positive outcome, the sensitivity and specificity of this screening method were 100% and 99.1%, respectively. Conclusions: Cardiac symptoms are common after the second dose of BNT162b2 vaccine, but the incidences of significant arrhythmias and myocarditis are only 0.1%. The serial ECG screening method has high sensitivity and specificity for significant cardiac adverse effect but cost effect needs further discussed.

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