Journal of Pediatric Cardiology and Cardiac Surgery 8(2): 60‒64 (2024)

Review[JSPCCS 59th Annual Conference]

ECG Screening for BNT162b2 COVID Vaccine Related
Cardiovascular Adverse Effects in School-Aged Students
Shuenn-Nan Chiu, MD, PhD1), Yih-Sharng Chen, MD, PhD2),
Yu-Chuan Hua, BS3), and Jou-Kou Wang, MD, PhD1)
1) Department of Pediatrics, National Taiwan University Hospital and Medical College, National Taiwan University, Taiwan2) Department of Surgery, National Taiwan University Hospital and Medical College, National Taiwan University, Taiwan
3) Cardiac Childrenʼs Foundation Taiwan, Taiwan

Since the COVID-19 outbreak in Wuhan, China in early 2020, the pandemic has become a major global
health concern. While vaccines are believed to be crucial for preventing COVID-19, there have been reports ofvaccine-related cardiac events, particularly peri-myocarditis. In collaboration with the Taipei City Government,
we conducted electrocardiogram (ECG) screenings to investigate the potential cardiovascular adverse effectsof the BNT162b2 COVID-19 vaccine in school-aged students. Among the 7934 eligible students, 4928 (62.1%)
completed both pre- and post-vaccine ECGs. The incidence of cardiac-related symptoms after the second dose
was 17.1%, with palpitations and chest pain being the most common symptoms. ECG parameters showeda significant increase in heart rate and a decrease in QRS duration, QT, QTc, and QTcf intervals after vaccination.
After comparing pre- and post-vaccine ECGs, 51 (1.03%) students were identified with significant ECG changes,
with ST-T changes being the most common. Further evaluation revealed that most adverse events were mildand did not require hospital admission. Sensitivity and specificity analysis indicated that the serial comparison
method was the most appropriate screening approach for post-vaccine cardiac adverse events. However, a
cost-benefit analysis would be essential for further consideration. The study highlights the importance of paired
ECG screening as a potential tool to serve as a reference for future medical events that may require screening.

Keywords: ECG, screening, BNT162b2 vaccine, myocarditis, arrhythmia

ECG Screening for School-Aged Children
Similar to Japan, Taiwan has been conducting along-term cardiac screening program for school-aged
children with the support of the Cardiac Children Foundation, Taiwan. The main method used for cardiac screeningin school-aged children was electrocardiography (ECG),
which has shown significant effectiveness. Numerous
studies have been published in this field, including research
on Cardiac conduction disturbance detected in a pediatricpopulation, long-term outcomes of pediatric sinus bradycardia, and cardiac screening for high risk sudden cardiac

death in school-aged children.1‒3)

COVID-19 Pandemics and Vaccination
The COVID-19 pandemic has had a tremendous
impact on human life worldwide over the past three
years. This global outbreak has not only caused a large
number of infections and deaths but has also fundamentally changed human lifestyles. Over the past two
years, Taiwanʼs government has effectively controlled
the infection rate, resulting in relatively fewer cases ofinfection.4) However, with the emergence and spread of
the Omicron variant, the number of confirmed cases has

J-STAGE Advance Published Online: June 20, 2024
Corresponding author: Shuenn-Nan Chiu, MD, PhD, Department of Pediatrics, National Taiwan University Hospital, No. 7,
Chung-Shan South Road, Taipei 100225, Taiwan
E-mail: michael@ntuh.gov.tw
Shuenn-Nan Chiu ( https://orcid.org/0000-0001-5559-1651)
doi: 10.24509/jpccs.23-015© 2024 Japanese Society of Pediatric Cardiology and Cardiac Surgery
This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/)

61

surged, and it was estimated that more than one-thirdof the population in Taiwan has been infected with
COVID-19 by 2022.4) Similar to other countries, we alsorelied on vaccines as the primary tool to prevent severecases of COVID-19.5) However, heart-related side effects
have been observed from vaccines after large-scalevaccination campaigns. In June 2021, the U.S. Food andDrug Administration (FDA) issued a warning indicatingthat mRNA vaccines may cause myocarditis, particularly
more commonly observed in young individuals.6, 7) The
U.S. CDCʼs Adverse Event Reporting System compiled
cases possibly related to vaccine-induced myocarditis.5)
It was found that the prevalence of myocarditis washighest in males after receiving the second dose of thevaccine, particularly in young individuals aged 12 to 24
years, with an estimated occurrence of 52 to 105 cases
per million people.8) In the nationwide prevalence study
conducted in Israel, it was similarly observed that males
between the ages of 16 and 24 had the highest incidenceof myocarditis, with an estimated rate of 15 cases per
100,000 people. When taking background rates into
account, the myocarditis incidence could potentially
increase by 5.3 times.9) Furthermore, regarding thetiming of occurrences, they also found that the highest
incidence of myocarditis was observed within two toseven days after receiving the second dose of the vaccine.10)

Background of Screening for Post-Vaccine
Cardiac Adverse Eﬀects
Due to the negative news surrounding these vaccines, there was significant resistance among the public,
students, and parents towards receiving vaccinations,especially in the context of the governmentʼs preparations for large-scale administration of the BNT162b2
vaccine on the younger population. Therefore, we
endeavored to explore potential measures for early
detection of myocarditis cases. However, when we proposed the plan of implementing ECG screening to detect
cardiovascular adverse effects in school-aged children,
we encountered numerous doubts and inquiries. Let us
now examine the key questions to determine the feasibility and value of conducting such a screening program.
Doctor Kaltman have defined the key questions fordetermining whether it is worthwhile to conduct a
screening program.11) First, it should be an important
issue and, we need to identify the high-risk populationand focus on screening these individuals. Secondly, wemust have effective screening tools that are accurate,easy to use, non-invasive, affordable, and capable ofearly detection. Thirdly, the screened disease should betreatable, and early intervention should lead to improved
survival rates.
In addressing the first aspect, BNT162b2-related
myocarditis represents a significant public healthconcern that can impact vaccination rates. The high-risk
group has been pinpointed as the young male population following the administration of the second
vaccine dose. Regarding the third aspect, timely identification and early treatment of myocarditis can reducemorbidity and mortality. Turning to the second aspect,
the disease typically manifests two days after receiving
the vaccine, affording us a crucial window for screening.
Consequently, there is a justified need for screening forpost-vaccine myocarditis. However, determining the
optimal and cost-effective screening tool remains to beelucidated.

Screening Tools of Post-Vaccine Cardiac
Adverse Eﬀects
Firstly, we need to understand how myocarditis isdiagnosed. In 2021, the U.S. Centers for Disease Control and Prevention (CDC) redefined the diagnostic
criteria for myocarditis cases.6) For potential cases, one
symptom (chest pain, shortness of breath, palpitations,and fainting) must be present along with one laboratory
finding (elevated cardiac enzymes, abnormal electrocardiogram, impaired cardiac function, and magnetic resonance imaging consistent with myocarditis). For confirmed cases, one symptom and either histopathologicalconfirmation or elevated cardiac enzymes with magnetic
resonance imaging diagnosis are required. As magnetic
resonance imaging and echocardiography is relatively
expensive, more favorable screening tools may include
symptom screening, blood tests for cardiac enzymes, orelectrocardiogram screening.
At that time in Taiwan, the government provided
each vaccine recipient with an informational leaflet,highlighting symptoms to watch out for. However, asignificant proportion of individuals experienced cardiac-related symptoms after vaccination. Therefore,
whether other screening methods, such as electrocardiogram screening, can be used to detect cardiac-related
complications in school-aged adolescents early after© 2024 Japanese Society of Pediatric Cardiology and Cardiac Surgery

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vaccination, is a focal point of our research.

Screening Method for Post-Vaccine Cardiac
Adverse Eﬀects
In Taiwan, there is a specific process for administering the COVID-19 BNT162b2 vaccine to school-aged
children. All high school students in the same school
received the BNT162b2 vaccine on the same day within
the school premises. Additionally, the vaccination
schedule was tightly packed, with all high school students across the country receiving their first dose of thevaccine within two weeks, followed by the second dose
after 12 weeks, completed within another two weeks.
Therefore, our research design involved conducting
the first questionnaire survey and performing pre-vaccination electrocardiogram (ECG) examinations before
administering the 2nd dose of the vaccine.12) After theadministration of the second dose of the BNT162b2
vaccine, we conducted the second questionnaire survey
and perform ECG examinations once again, followed
by a comparison of the ECG readings before and after
vaccination.
Fig. 1 is an on-site photo where we have set up theschoolʼs sports center with 50 partitions, each equippedwith an operator and an electrocardiogram (ECG)
machine. Consequently, we could conduct ECG examinations for 50 students simultaneously. We used PCA
500 12-lead ECG recorder (QT Medical Inc.). ECG data
were transferred wirelessly to the cloud (QT Cloud; QT
Medical Inc.) and analyzed using an ECG diagnostic
system (QTM-DX; QT Medical, Inc.). The ECG data was

Table 1

The criteria of signiﬁcant ECG change set forserial comparison of pre- and post-vaccine
ECGs by QTM-DX

Premature ventricular beats (PVC)
New PVC detected
Number of PVCs increase more than 2
PVC couplets, triplets or runs
More than 2 PVC morphologies
Premature atrial beats (PAC)
New PAC detected
Number of PACs increase more than 2
PAC couplets, triplets or runs
Heart rate change
Heart rate increase >20 beats per minute (bpm) and current heart rate >100 bpm
Heart rate decrease >20 bpm and current heart rate
<60 bpm
Extreme sinus bradycardia
Heart rate below 40bpm
Atrial arrhythmia
New atrial ﬁbrillation, ﬂutter, or tachycardia detected
Atrioventricular blockPR interval increase >30 ms
2nd or complete atrioventricular block
Bundle branch block or intraventricular conduction delay
New right bundle branch block detected
New left bundle branch block detected
QRS duration increase >15 ms and QRS duration >110 ms
Q wave change
Q wave duration≥20 ms at lead V2, V3
Q wave duration≥30 ms and Q wave amplitude >0.1 mV
at other leads
QS complex in contiguous leads
QRS change
QRS axis change by >45 degrees
Sum of limb leadsʼ (R+S) decrease by >30%
Sum of chest leadsʼ (R+S) decreased by >30%
ST change
ST elevated ≥0.2 mV compared to the baseline
ST depressed ≥0.2 mV compared to the baseline
T wave change
New T wave inversion detected
T wave amplitude >10 mm
Prolonged QT
QTc interval increase >20 ms
QTc interval >470 ms
Courtesy provided by Chiu SN, et al. Eur J Pediatr 2023:
1‒8.12)first checked by QTM-DX analyzer and doubly checkedby pediatric cardiologists on the web. The pre- andpost-vaccine ECGs were compared using the serial comparison function of QTM-DX. Table 1 shows the criteriaof the significant ECG change.
Fig. 1 National Taiwan University Hospital collaborated with the Taipei City Government to
conduct electrocardiogram (ECG) screenings
in four senior high schools
Courtesy provided by Chiu SN, et al. Eur J Pediatr
2023: 1‒8.

J Pediatr Cardiol Card Surg Vol. 8, No. 2 (2024)

Results of ECG Screening for Post-Vaccine
Cardiac Adverse Eﬀects
Among 7934 eligible students, 4928 (62.1%) completed both pre- and post-vaccine ECGs (Fig. 2). The
male-to-female ratio was 13 : 1, and the mean age was

63Fig. 2 The ﬂow chart and outcome of the ECG screening for cardiac adverse eﬀects after 2nd dose of BNT162b2
vaccinesen=sensitivity, spe=speciﬁcity.

16.7± 0.9 years. Underlying medical conditions were
present in 109 (2.2%) of the participants, with simple
congenital heart disease, mitral valve prolapse, andarrhythmia being the most common.
From the questionnaire, the incidence of cardiac-related
symptoms was 5.7% after the 1st dose and 17.1% after thesecond dose of the BNT162b2 vaccine, with palpitations
and chest pain being the most common symptoms.
When comparing ECG parameters, there was a significant increase in heart rate after the vaccine, with a mean
increase of 2.6 beats per minute (bpm). Additionally, the
QRS duration, QT, QTc, and QTcf intervals all decreased
significantly after the vaccine. Based on serial comparisons of pre- and post-vaccine ECGs, 51 (1.03%) students
were identified as having significant ECG changes after
vaccination. ST-T changes were the most common,present in 72.5% of the students, followed by arrhythmia(13.7%), bundle branch block (5.9%), and abnormal
QRS (3.9%) and QT intervals (3.9%). Hospital transfer
was arranged for these patients, and 5 of them weredeemed to have significant adverse events. One student
had subclinical myocarditis with premature ventricularbeats, and although his troponin T level increased to
19 ng/L, it spontaneously recovered without admission.
The other 4 students had arrhythmia, with 2 experiencing
sinus bradycardia, 1 with atrial tachycardia, and 1 withpremature ventricular beats.12) Among the remaining
4877 students with negative screening results, detailed
information on post-vaccine cardiac adverse effects wascollected from school nurses and the school vaccination

reporting system of the Health Bureau of Taipei City
government 1 month after vaccination. All these students
were confirmed to have no adverse cardiac events requiring hospital admission.

Accuracy and Cost Analysis
We also conducted sensitivity and specificity analysis
and compared different screening methods, including
serial comparison as used in this study, post-vaccine
ECG screening alone, and post-vaccine ECG combinedwith any cardiac symptoms. The serial comparison
method showed a sensitivity of 100%, specificity of
99.1%, positive predictive value 9.8% and negative
predictive value 100%. When using post-vaccine ECG
screening alone, the specificity dropped to 86%, resulting in a low positive predictive value of 0.72%. The
addition of cardiac symptoms in the post-vaccine ECG
increased the specificity to 97.5%, but the sensitivity
dropped to 20% and positive predictive value remained
low 0.79%. Therefore, the serial comparison method is
the most appropriate screening approach for detecting
post-vaccine cardiac adverse events.12) We then performed a cost and benefit analysis, revealing that thescreening cost was US$14.3 per student, meaning thecost to identify a case of cardiovascular adverse eventswas US$14,094. However, as indicated in the current
study and previous reports, most adverse events weremild. Utilizing data from the Israel nationwide survey
study, detecting a case of severe myocarditis would incur
an expense of US$430,462.12)© 2024 Japanese Society of Pediatric Cardiology and Cardiac Surgery

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Other Screening Tools

References

Apart from electrocardiogram (ECG) screening,are there any other screening methods available? In
one Israeli hospital, a before-and-after comparison
trial was conducted on healthcare workers receiving
the fourth dose of the COVID-19 BNT162b2 mRNA
vaccine.13) Blood samples were taken to test for Troponin T levels before and after vaccination. Amongthe 324 participants, two individuals showed a slightincrease in Troponin T levels, but both values were
<25 ng/L. Furthermore, subsequent ultrasound, ECG,
and magnetic resonance imaging examinations for thesetwo participants were all normal. This finding further
demonstrates that most myocardial injuries caused by
the BNT162b2 vaccine are relatively mild.

1) Chiu SN, Wang JK, Wu MH, et al: Taipei Pediatric
Cardiology Working Group: Cardiac conduction
disturbance detected in a pediatric population. J Pediatr
2008; 152: 85‒892) Chiu SN, Lin LY, Wang JK, et al: Long-term outcomes ofpediatric sinus bradycardia. J Pediatr 2013; 163: 885‒889.
e13) Liu HW, Huang LW, Chiu SN, et al: Cardiac screening forhigh risk sudden cardiac death in school-aged children.
Acta Cardiol Sin 2020; 36: 641‒6484) Taiwan Centers for Disease Control: Prevention and Control of COVID-19 in Taiwan. 2021. https://www.cdc.gov.
tw/En/Category/Page/0vq8rsAob_9HCi5GQ5jH1Q
5) Gargano JW, Wallace M, Hadler SC, et al: Use of mRNA
COVID-19 vaccine after reports of myocarditis among
vaccine recipients: Update from the Advisory Committee
on Immunization Practices̶United States, June 2021.
MMWR Morb Mortal Wkly Rep 2021; 70: 977‒982
6) Centers for Disease Control and Prevention (CDC): Advisory Committee on Immunization Practices (ACIP). Coronavirus disease 2019 (COVID-19) vaccines. 2021. https://www.
cdc.gov/vaccines/acip/meetings/slides-2021-2006.html
7) Marill MC: FDA to add myocarditis warning to mRNA
COVID-19 vaccines. Medscape, 2021. https://www.
medscape.com/viewarticle/953647
8) Oster ME, Shay DK, Su JR, et al: Myocarditis cases
reported after mRNA-based COVID-19 Vaccination in
the US from December 2020 to August 2021. JAMA 2022;
327: 331‒3409) Mevorach D, Anis E, Cedar N, et al: Myocarditis after
BNT162b2 mRNA Vaccine against Covid-19 in Israel. N
Engl J Med 2021; 385: 2140‒2149
10) Witberg G, Barda N, Hoss S, et al: Myocarditis after
Covid-19 vaccination in a large health care organization.
N Engl J Med 2021; 385: 2132‒2139
11) Kaltman JR, Thompson PD, Lantos J, et al: Screening
for sudden cardiac death in the young: Report from anational heart, lung, and blood institute working group.
Circulation 2011; 123: 1911‒1918
12) Chiu SN, Chen YS, Hsu CC, et al: Changes of ECG parameters after BNT162b2 vaccine in the senior high school
students. Eur J Pediatr 2023; 182: 1155‒1162
13) Levi N, Moravsky G, Weitsman T, et al: A prospective
study on myocardial injury after BNT162b2 mRNA
COVID-19 fourth dose vaccination in healthy persons.
Eur J Heart Fail 2023; 25: 313‒318

Conclusion
Although cardiac-related symptoms were common,
the incidence of myocarditis, even subclinical cases,
was very low. The ECG parameters of depolarization
and repolarization exhibited no significant abnormalchanges, and arrhythmias were rare after vaccinationin this healthy young population. ECG screening withpre- and post-vaccine comparison demonstrated highsensitivity and specificity. Nevertheless, cost and benefit considerations needed to be justified. However, thisECG screening method can serve as a reference for
future medical events that may require screening.
Conﬂicts of Interest
None.
Author Contribution
Shuenn-Nan Chiu conceptualized the study, collected thedata, analyzed the initial study, drafted and reviewed andrevised and final proved the manuscript Yih-Sharng Chen,
Yu-Chuan Hua, and Jou-Kou Wang: conceptualized anddesigned the study, coordinated and collected the data, analyzed the initial study, and reviewed and revised and final
proved the manuscript.

J Pediatr Cardiol Card Surg Vol. 8, No. 2 (2024)