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August 30th, 2021
SARS-CoV-2 mRNA Vaccination-Associated Myocarditis in Children
Ages 12-17: A Stratified National Database Analysis
Authors: Tracy Beth Høeg MD, PhD1; Allison Krug, MPH2; Josh Stevenson3; John Mandrola,
MD4
Affiliations:
1. University of California - Davis, Sacramento, CA
2. Artemis Biomedical Communications, LLC, Virginia Beach, Virginia, USA
3. Truth in Data, LLC, Nashville, Tennessee, USA
4. Baptist Health Louisville, Louisville KY
Corresponding Author email: tracybethhoeg@gmail.com
Corresponding Author: 4860 Y St #1700, Sacramento, CA 95817; (916) 734-7041
Funding: None
Keywords: myocarditis, mRNA, vaccination, COVID-19, pediatrics, drug-related side effects
and adverse reactions
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SARS-CoV-2 mRNA Vaccination-Associated Myocarditis in Children Ages 12-17:
A Stratified National Database Analysis
ABSTRACT
Objectives: Establishing the rate of post-vaccination cardiac myocarditis in the 12-15 and 16-17-
year-old population in the context of their COVID-19 hospitalization risk is critical for
developing a vaccination recommendation framework that balances harms with benefits for this
patient demographic.
Design, Setting and Participants: Using the Vaccine Adverse Event Reporting System
(VAERS), this retrospective epidemiological assessment reviewed reports filed between January
1, 2021, and June 18, 2021, among adolescents ages 12-17 who received mRNA vaccination
against COVID-19. Symptom search criteria included the words chest pain, myocarditis,
pericarditis and myopericarditis to identify children with evidence of cardiac injury. The word
troponin was a required element in the laboratory findings. Inclusion criteria were aligned with
the CDC working case definition for probable myocarditis. Stratified cardiac adverse event
(CAE) rates were reported for age, sex and vaccination dose number. A harm-benefit analysis
was conducted using existing literature on COVID-19-related hospitalization risks in this
demographic.
Main outcome measures: 1) Stratified rates of mRNA vaccine-related myocarditis in
adolescents age 12-15 and 16-17; and 2) harm-benefit analysis of vaccine-related CAEs in
relation to COVID-19 hospitalization risk.
Results: A total of 257 CAEs were identified. Rates per million following dose 2 among males
were 162.2 (ages 12-15) and 94.0 (ages 16-17); among females, rates were 13.0 and 13.4 per
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million, respectively. For boys 12-15 without medical comorbidities receiving their second
mRNA vaccination dose, the rate of CAE is 3.7 to 6.1 times higher than their 120-day COVID-
19 hospitalization risk as of August 21, 2021 (7-day hospitalizations 1.5/100k population) and
2.6-4.3-fold higher at times of high weekly hospitalization risk (7-day hospitalizations 2.1/100k),
such as during January 2021. For boys 16-17 without medical comorbidities, the rate of CAE is
currently 2.1 to 3.5 times higher than their 120-day COVID-19 hospitalization risk, and 1.5 to
2.5 times higher at times of high weekly COVID-19 hospitalization.
Conclusions: Post-vaccination CAE rate was highest in young boys aged 12-15 following dose
two. For boys 12-17 without medical comorbidities, the likelihood of post vaccination dose two
CAE is 162.2 and 94.0/million respectively. This incidence exceeds their expected 120-day
COVID-19 hospitalization rate at both moderate (August 21, 2021 rates) and high COVID-19
hospitalization incidence. Further research into the severity and long-term sequelae of post-
vaccination CAE is warranted. Quantification of the benefits of the second vaccination dose and
vaccination in addition to natural immunity in this demographic may be indicated to minimize
harm.
INTRODUCTION
Pfizer-BioNTech BNT162b2 and Moderna mRNA-1273 vaccines for SARS-CoV-2 have
demonstrated exceptional safety and real-world effectiveness in preventing severe disease and
death from COVID-19. Concerns about vaccination-related myocarditis in young men were
initially raised in Israel with rates between 1/3000-1/6000.[1] In the United States, the initial
Centers for Disease Control and Prevention (CDC) report[2,3] identified a rate of approximately
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12.6 per million (1/80,000) second doses administered in ages 12-39, but approximately
1/15,000 for males 12-17 and 1/19,000 for males 18-24.[2,3]
Although the CDC analyses [2,3] identified a higher rate of myocarditis in boys than young men,
further stratification by adolescent age group (e.g., 12-15 and 16-17 years) was not provided. A
second potential limitation was the sensitivity of the CDC symptom search inclusion criteria,
which may have failed to identify cases of cardiac adverse events (CAEs), consistent with
myocarditis, with objective evidence of cardiac injury following vaccination.
On August 23rd, the Federal Drug Administration (FDA) released a Pfizer-BioNTech vaccine
report[4] which outlines “an excess risk [of myocarditis] approaching 200 cases/million” or
1/5000 in 16–17-year-old boys, which was three times higher than reported by the CDC [2,3]. In
their harm-benefit analysis, the most likely scenario was the benefits of vaccination would
outweigh harms in 16-17-year-old males, but “predicted excess cases of vaccine-associated
myocarditis/pericarditis would exceed COVID-19 hospitalizations and deaths under the ‘worst
case’ scenario” [4].
Post-vaccination myocarditis rates for the 12-15-year-old age group had not yet been reported
beyond the initial trial with 1131 vaccination recipients [5], until August 30th, 2021, when the
CDC reported [6] the following rates for boys ages 12-15 and 16-17 within seven days of their
second dose of Pfizer-BioNTech at 42.6 and 71.5 per million, respectively. For females, rates
were 4.3 and 8.1 per million, respectively. A harm-benefit analysis of vaccination in the pediatric
age group has not yet been performed based on presence of absence of underlying medical
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conditions. While medical comorbidities confer higher risk for severe COVID-19, this is not
known to be the case for post-vaccination myocarditis.
The CDC [2,6] reported a 94-96% hospitalization rate for VAERS-identified myocarditis. The
CDC used a 120-day COVID-19 hospitalization rate as a meaningful comparator to vaccination-
related harms, and we have chosen to use this same comparison for our study.
Our primary aim was to stratify post-mRNA vaccination myocarditis by age and vaccination
dose within the 12–17-year-old population. Our secondary aim was to provide an updated
estimate to complement the CDC’s [2,3,6] and FDA’s [4] findings. Our final aim was to perform
a harm-benefit analysis of mRNA COVID-19 vaccination myocarditis with that of COVID-19
hospitalization for children with and without one or more comorbidity at low, moderate, and high
120-day COVID-19 hospitalization rates.
METHODS
We searched the Vaccine Adverse Event Reporting System (VAERS) data for females and males
ages 12-17 in reports processed from 1/1/2021 through 6/18/2021 with diagnoses of
“myocarditis,” “pericarditis,” “myopericarditis” or “chest pain” in the symptom notes and
required the term “troponin” in the laboratory data. We defined a CAE using the CDC working
case definition for a probable case.[2] Specifically, the symptom of “chest pain” required at least
one of the following: diagnosis of myocarditis, peri- or myopericarditis, acute myocardial
infarction; elevated troponin; abnormal electrocardiogram (EKG), abnormal echocardiogram
(ECHO), or cardiac MRI (cMRI) findings consistent with myocarditis (as defined in Supplement
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1). Cases and hospitalizations with an unknown dose number were assigned to dose 1 or dose 2
in the same proportion as the known doses: 15% occurred following dose 1 and 85% occurred
following dose 2.
To compute crude rates per million for doses 1 and 2, our denominators included all children
with at least 1 dose of any vaccination and all fully vaccinated children, respectively, as of
6/11/2021[6] to accommodate both reporting lag and a pre-defined 7-day risk window, consistent
with the CDC’s analysis. 95% Poisson confidence intervals were calculated for these rates.
To perform a harm-benefit analysis, pediatric hospitalization rates for COVID-19 were obtained
from the CDC’s COVID-NET.[7] COVID-19 hospitalization rates among children with and
without one or more medical comorbidities were calculated based on hospitalization rates at
times of low (June 2021), moderate (August 2021) and high (January 2021) incidence.[8]
Children with at least one medical comorbidity were considered to have 4.7 times the likelihood
of COVID-19 hospitalization as those without comorbidities based on 70% of children
hospitalized for COVID-19 having one or more medical comorbidity.[9] We estimate 33% of
children in this age group have one or more comorbidity based upon current data[10] suggesting
21.2% of children 12-19 have obesity and around 8.4% have asthma.[11] These comorbidities
are also found in the summary of underlying conditions for pediatric COVID-19 hospitalizations
reported to COVID-NET.[8] The two most common underlying conditions among pediatric
hospitalizations are obesity (33.8%) and asthma (14.8%).[8] Other relevant comorbidities such as
diabetes[11] or the medically complex children[12] appear to make up <5% of this
demographic.[11] The estimated ratio of expected hospitalizations for children by presence or
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absence of comorbidity must therefore account for the relative proportions of children with and
without comorbidities in the population, and among those admitted for COVID-19. The
computation is as follows: [(0.67/0.33) / (0.3/0.7) = (0.67*0.7) / (0.33*0.3) = 0.469 / 0.099 =
4.7], in other words a 4.7-fold difference in hospitalization risk for children with and without
medical comorbidities.
We provided an additional rate which adjusted for the reported approximate 40% of pediatric
hospitalizations for COVID-19 being incidental positive tests on admission.[9,13,14] Finally,
the risk of post-vaccination CAE post-dose two in 12–15-year-old-boys was compared with their
overall risk of hospitalization from COVID-19 according to presence or absence of comorbidities
and adjusted for the 40% hospitalization overestimate as well as the asymptomatic fraction of
pediatric cases.
Data were analyzed using Microsoft PowerBI, Stata and Microsoft Excel
RESULTS
A total of 276 reports met our initial search criteria; of these, 18 were excluded because they had
no objective evidence of elevated troponins or abnormal findings on ECG/EKG or ECHO, or we
could not exclude the possibility of viral myocarditis or concomitant pneumonia. Of the 18
excluded cases, eight were hospitalized. Nine were 12-15 and nine were 16-17 years old. Sixteen
of the excluded cases were coded “chest pain” in the symptom notes and the remaining two
females were coded as “myocarditis” but no troponin values nor EKG/ECG findings were
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included. Of the remaining 258 cases, we excluded from sex-specific rates one case with
“unknown” sex, leaving 257 cardiac adverse event reports for full analysis (25 females and 232
males). Of these, 211 cases had peak troponin values available for analysis (Supplement 2); 37
reports did not include the vaccine dose number. Of the 257 included cases, 256 had received
Pfizer-BioNTech mRNA vaccination, one had received Moderna mRNA vaccination (only
Pfizer-BioNTech was approved for vaccination of children <18 at the time of our database
search).
The CAE rates by age and sex and vaccination dose are shown in Figure 1 and Table 1.
(Interactive data visualizations and full VAERS case notes available at this link:
https://bit.ly/CAEmRNA). Our post-second-dose-vaccination rates of CAE among adolescent
boys aged 12-15 was 162.2/million which exceeded the rates reported by the CDC[2,6] by 143-
280% (2.4-3.8 times). Among boys age 16-17, our estimate was 94.0/million, 31.5-41% higher
than the CDC estimate. For girls 12-15 years old, our rate was 13.0/million, which was 43-100%
higher that the CDC’s estimate.[2,6] Among girls 16-17, our estimate was 13.4/million, which
was 47-65% higher than the CDC’s estimate.
Rates per million following dose 1 among males were: 12.0 per million (ages 12-15) and 8.2 per
million (ages 16-17). Rates per million following dose 1 among females were 0 (ages 12-15) and
2.0 (ages 16-17). With respect to dose 1 and compared to CDC findings, 12–15-year-old boys
were 22-150% higher than the CDC, while girls this age had zero CAEs in our analysis. Among
adolescents ages 16-17, our rates were 16% lower to 58% higher for boys and 82% higher for
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girls [2] and in the updated CDC report [6] the reported rate for girls 16-17 post-dose one was
0.0 per million.
The CAE cases in our investigation occurred a median of 2 days following vaccination, and
91.9% occurred within 5 days. The reported CAE hospitalization rate for our study group was
222/257 (86.4%); 112/130 (86.2%) in the 12–15-year-old cohort and 110/127 (86.6%) in the 16–
17-year-old cohort (Figure 2). Specific hospitalization rates for boys were 106/122 (86.9%) for
the 12–15-year-old boys and 96/110 (87.3%) for the 16–17-year-old boys (Figure 2).
The median peak troponin T/I (Figure 3) (normal <0.1 ng/mL) was 5.2 ng/mL in boys ages 12-
15 and 11.6 ng/mL in boys ages 16-17; for girls, the medians were 0.8 ng/mL and 7.3 ng/mL,
respectively. Peak troponin values exceeded 2 ng/mL for 71% of cases age 12-15 and 82% of
cases age 16-17. Figure 4 shows the time course of troponin increases after vaccination: 183/211
(86.7%) measured as elevated within 4 days. For the 221 cases for which the dose number was
available, 32 (15%) occurred after dose 1 and 189 (85%) occurred after dose 2. The 37 cases
with an unknown dose number were assigned proportionately to the overall distribution among
the cases with a known dose number: 5 were assigned to dose one and 32 were assigned to dose
two.
COVID-19 hospitalization vs. vaccination harms
In the seven-month period of January 2021-July 2021, the rate of COVID-19 hospitalization
among adolescents (ages 12-17) has ranged from a low of ≤ 4 per million weekly (July 2021) to
moderate level (15 per million per week in mid-August 2021) and high (21 per million per week
in January 2021) (Figure 6).[8,9] A healthy adolescent might expect a COVID-19 hospitalization
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risk of 44.4 per million over the next 120 days, assuming disease-related hospitalization
prevalence stays at moderate levels (Figure 6, Figure 7). A child with at least one comorbidity
might expect a disease-associated hospitalization rate of 210.5 per million per 120 days during
times of moderate hospitalization, with a peak hospitalization risk of 294.7 per million per 120-
days if rates surge to the same high level as January 2021.
At times of low adolescent COVID-19 hospitalization rates, such as in June 2021, a CAE from
the second dose of an mRNA vaccine in a healthy 12–15-year-old boy was 13.7-fold more likely,
at 162.2 per million, than the 120-day risk of COVID-19 hospitalization. The rate of post-
vaccination CAE for boys 12-15 years without comorbidities (162.2/million) receiving their
second vaccination dose exceeds their current 120-day COVID-19 hospitalization risk
(44.4/million) by 3.7 times. In 16–17-year-old boys without comorbidities, the risk of post-dose
two vaccination CAE exceeds their current 120-day hospitalization risk by 2.1 times
(94.0/million vs. 44.4/million per 120-days). Our estimated risk of post-second vaccination dose
CAE hospitalization for boys 12-15 without medical comorbidities (141/million; based on 86.9%
hospitalization rate) also exceeds that of their 120-day COVID-19 hospitalization risk even at
high hospitalization rates (Figures 6 and 7). For 12–17-year-old-boys with at least one medical
comorbidity (Figure 6 and 7) their risk of post-vaccination CAE only exceeds their 120-day
COVID-19 hospitalization risk at times of low hospitalization rates.
We also performed an adjusted analysis based on 40% of COVID-19 hospitalizations being due
to another cause with incidental positive COVID-19 test during the hospitalization [8,12,13]. At
current moderate incidence, the 120-day hospitalization risk for COVID-19 for a healthy child
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may be as low as 26.7 per million (Figure 6 in italics), twice the risk of a CAE after vaccine dose
1 in boys without comorbidities and after dose 2 in girls without comorbidities (Table 1). The
risk for boys aged 12-15 with no comorbidities of CAE after dose two would be 22.8 times
higher than their COVID-19 hospitalization risk at the adjusted low (7.1/million), 6.1 times
higher for moderate (26.7/million) and 4.3 times higher at high (37.3/million) 120-day
hospitalization rates (Figures 6 and 7). The risk for boys 16-17 with no comorbidities of CAE
after dose 2 would be and 13.2 times higher than their COVID-19 hospitalization risk at the
adjusted low (7.1/million), 3.5 times higher at moderate (26.7/million) and 2.5 times higher at
high (37.3/million) 120-day adjusted hospitalization rates (Figures 6 and 7). For 12–15-year-old
boys with one or more comorbidity, the vaccine-associated CAE risk following dose two is less
than the adjusted COVID-19 hospitalization risk at times of high COVID-19 incidence. For 16–
17-year-old boys with one or more comorbidity, the CAE rate was below that of the adjusted
COVID-19 hospitalization risks at both current (moderate) and high disease prevalence (Figure
7; Table 1).
DISCUSSION
Principal findings
The main finding of this study was the cardiac adverse event (CAE) rates of 162/million and
94/million post- Pfizer-BioNTech BNT162b2 vaccination dose two for the 12-15- and 16–17-
year-old boys, respectively. Approximately 86% of these resulted in hospitalization for both age
groups. We included a case-finding method in VAERS which utilized the symptom “chest pain”
to identify adolescents for review of troponins, EKG/ECG and ECHO findings. We otherwise
maintained the specificity of our analysis by requiring the same objective findings of cardiac
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injury used by the CDC to identify probable cases (Supplement 1) and excluded cases without
sufficient objective evidence of cardiac-specific injury.
Using these broader search and inclusion criteria, we found post-vaccination rates of CAEs
among adolescents aged 12-17 that exceeded the rates previously reported by the CDC[2] by 2.5
times in boys aged 12-15 and by 1.7 x in 16-17-year-old boys. Our results show the risk of
myocarditis depends heavily on sex and age, as it appears that young boys 12-15 have a greater
than 12 times higher rate than girls. Due to a markedly increased risk for the youngest boys,
prospective safety analyses would be most useful if stratified by ages 12-15 years and 16-17
years.
The highest troponin elevations were seen in the 16–17-year-old boys and girls. In the setting of
cardiac symptoms, children with elevated troponin levels have a high likelihood of cardiac
disease.[17, 18] Of note, the threshold for normal levels in children may be even lower than the
0.1 ng/mL used in adults.[17]
To contextualize the benefits of vaccination for adolescents, we chose, as the CDC did [2,3] to
provide a benefit-harm analysis based on varying levels of COVID-19 hospitalization rates.[19]
Our analysis not only considered circulating disease levels but also the presence of individual
risk factors for severe disease. A weakness of our analysis was not being able to stratify
hospitalization risks for children with and without natural immunity. The CDC estimated that on
May 29th, 2021, that 36.2% [15] of all children had already been infected with SARS-CoV-2.
This estimate was made 16 months into the pandemic, thus adjusting for the current time (19
months), the current estimate would be (19/16)*36.2% = 42.9% of children previously infected.
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Absolute infection-hospitalization rates for children with and without medical comorbidities and
with and without history of infection have yet to be established.
In a recent report[20] of 15 patients aged 12-18 hospitalized with post-vaccination myocarditis,
the clinical course was reported to be relatively benign, but 1/15 had abnormal echocardiogram
on follow-up and 4/15 had ongoing symptoms post-discharge. The CDC reported [2] that 218 of
the 323 (67.5%) cases of myo/pericarditis in vaccine recipients <30 years were known to have
had resolution of symptoms. Another study[21] found 16/23 (70%) males with vaccination-
associated myocarditis to have had resolution of symptoms within a week. Long-term sequalae
of myocarditis is unknown; follow-up of this vaccine-associated condition is warranted.
COVID-19 has also been found to result in symptomatic myocarditis in 0.3% of collegiate
athletes,[22] but its rate in children post-COVID-19 infection has not been well described. The
one existing study[23] is limited by an inappropriately small denominator due to apparent
underestimate of COVID-19 disease incidence during the study period. The study[23] reported
only six post-COVID myocarditis cases in boys ages 12-17 over the course of a year in a 60-
million patient catchment area. Children have in general been spared from the worst effects of
COVID-19. The reported mortality rate in England has so far been 2/million children [24,25],
which may translate to around 6/million infections based on a prior infection rate of 1/3.[15] In
the US, there have been 4404 multisystem-inflammatory syndrome in children (MIS-C) cases in
a population of 74 million.[26] Long-duration of symptoms post-COVID-19 also appears less
frequent in children than initially feared, with 1.8% of children with symptomatic COVID-19
experiencing at least one symptom two months after infection compared with 0.9% of negatively
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tested controls after one month.[27] A thorough understanding of vaccine safety is thus crucial in
this age group, especially for children without known risk factors for severe COVID-19 and
those with history of infection. This report only outlines rates associated with the Pfizer-
BioNTech. A recent report from Canada [28] suggests a greater than 2-fold higher rate of post-
vaccination myocarditis from the Moderna mRNA vaccine compared to the Pfizer-BioNTech
mRNA vaccine. The most recent CDC update [6] also found Moderna to have higher rates of
post-vaccination myocarditis than Pfizer-BioNTech in all male age groups except those 16-17
years and those 65 and older.
A concern about using VAERS for our data analysis is the risk of over-ascertainment of a safety
signal due to the open access system. To address this concern, we aligned our inclusion criteria
with the CDC’s case definition for probable myocarditis. Our rate of myocarditis post-
vaccination of 94.0/million was more than two times lower than that reported by the FDA
(200/million) [2] and yet 31.5% higher than the CDC. This suggests that both VAERS and CDC
are providing an underestimate of the true incidence of this condition. Furthermore, the reports in
VAERS reviewed for this study were of children with myocarditis with cardiac symptoms and
not cases of incidental cardiac inflammation noted on imaging. It is thus unclear how large of an
underestimate of CAE incidence this report provides.
We, like the CDC, used a 120-day COVID-19 hospitalization rate as a meaningful comparator to
vaccination-related harms, but this type of harm-benefit analysis does not take into account any
benefits the vaccine provides against transmission to others, long-term COVID-19 disease risk or
protection from non-severe COVID-19 symptoms. With this in mind, the risk of CAE for a boy
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receiving his second dose of the vaccine is 2 to 6 times higher than the 120-day risk of
hospitalization in boys 12-17 without underlying medical conditions. For boys with medical
comorbidities, the 120-day COVID hospitalization rates are slightly higher than their rate of
CAE if not adjusting for possible 40% overestimate of hospitalization rates [9,13,14], in which
case the rate of CAE would be slightly higher than 120-day hospitalization [Figures 6 and 7].
As of the last week of August 2021, hospitalization rates for children ages 12-17 in the United
States continued to approximate the moderate rate shown in Figures 6 and 7.[8] Current pediatric
hospitalization rates are also a product of increasing natural infection and vaccination rates.
Overall pediatric case hospitalization rate from COVID-19 has been estimated by the CDC [15]
and American Academy of Pediatrics [19] to be 0.8-0.9%, irrespective of comorbidities and not
adjusting for possible 40% overestimate of hospitalization rates [9,13,14]. This rate has remained
consistent through August of 2021.
Given the nearly fivefold disparity in risk of hospitalization for adolescents with and without
comorbidities, it is important that the benefits of vaccination be clearly weighed and conveyed in
the context of the unique health risks of the individual and the household. The benefits of
vaccination in previously-infected children should be further studied and a harm-benefit analysis
performed. A history of SARS-CoV-2 infection may be found to provide similar or superior
immunity to vaccination [29]. A recent study [30] found a 4-fold increased risk of post-
vaccination myocarditis in those who had previously been infected with SARS-CoV-2.
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In light of the vaccine-associated cardiac harms described in this report, further research as well
as transparency about possible vaccine-related harms in relation to an individual child’s COVID-
19 risks is indicated. Alternate vaccination types, dosing or strategies, such as those that take a
history of infection into consideration, may eventually be found to be more appropriate in this
age group.
Conclusion
Our report found post-vaccination CAE rates following dose two of 162.2 and 94.0/million for
boys 12-15 and 16-17, respectively. For boys with no underlying health conditions, the chance of
either CAE, or hospitalization for CAE, after their second dose of mRNA vaccination are
considerably higher than their 120-day risk of COVID-19 hospitalization, even at times of peak
disease prevalence. The long-term consequences of this vaccine-associated cardiac inflammation
are not yet fully defined and should be studied. In lieu of pediatric vaccination mandates, the US
may: 1) consider gathering data on previous infection in this age group and/or 2) follow the
example of Germany,[31] Sweden [32], Norway [33] and the WHO[34] and hold off on
definitively recommending vaccination of low-risk children against COVID-19, or 3) offer one
dose to adolescents as the UK has just announced [35] while more information about risks,
benefits, harms and alternative dosing or vaccination strategies are studied and considered.
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17
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20
Figures
Figure 1. Cardiac Adverse Event (CAE) rate per million vaccinated persons, by age and sex and
vaccination dose
Figure 2. Total number of Cardiac Adverse Event (CAE) hospitalizations by age and sex
Figure 3. Median of Peak Troponin by age and sex in ng/mL
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21
Figure 4. Symptom onset interval of Cardiac Adverse Events in days following vaccination
among recipients with elevated troponin, by age
Figure 5. Vaccine recipients with cardiac adverse events by vaccination dose
UNK= unknown
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1
Table 1. Cardiac Adverse Event (CAE) rates per million adolescents following vaccination doses 1 and 2, by age and sex.
Females (n=25)
Males (n=232)
Dose 1 (95% CI)a
Dose 2 (95% CI)b
Dose 1 (95% CI)a
Dose 2 (95% CI)b
12-15 years
CAE Criteria met
0
8
22
100
Denominator*
1,834,687
616,511
1,834,687
616,511
CAE Rate per million
0
(0-0.20)
13.0
(5.6-25.6)
12.0
(7.51-18.2)
162.2
(132.0-197.3)
16-17 years
CAE Criteria met
3
14
12
98
Denominator*
1,471,878
1,042,863
1,471,878
1,042,863
CAE Rate per million
2.0
(0.42-5.96)
13.4
(7.34-22.5)
8.2
(4.21-14.2)
94.0
(76.3-114.5)
a Dose 1 denominator: at least 1 dose by June 11, 2021.
b Dose 2 denominator: fully vaccinated by June 11, 2021. Sex-specific denominator estimated by dividing total by 2.
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2
Figure 6. Harm-benefit analysis for second dose of mRNA vaccine vs. COVID-19 hospitalization for boys ages 12-17 in the context of
disease incidence and presence of >1 comorbidity.
Darker shading denotes vaccine-associated risk of myocarditis equivalent to or exceeds disease-associated hospitalizations.
Low:
4/mill weekly,
68/mill 120-day
(Wk ending
7/24/21)*
Moderate:
15/mill weekly,
255/mill 120-day
(Wk ending
8/21/21)*
High:
21/mill weekly,
357/mill 120-day
(Wk ending
1/9/21)*
Hoeg, et al.*
Adj for incidental
admissions of 40%
7.1 26.7 37.3
At least 1 56.1 210.5 294.7
Adj for incidental
admissions of 40%
33.6 126.3 176.8 *Range is 94.0 (ages 16-17) to 162.2 (ages 12-15).
Number of
Comorbidities
None
11.8
44.4
62.2
Expected Risk-Adjusted 120-day Cumulative COVID-19
Hospitalizations per Million at Low, Moderate, and High
Weekly Prevalence
Vaccine-Associated Myocarditis
post dose 2 (boys only)
CDC Estimate
All Vaccinated
Children
94.0-162.2
66.7
*Source: CDC COVID-NET https://gis.cdc.gov/grasp/COVIDNet/COVID19_3.html
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3
Figure 7. Harm-benefit analysis for second dose of mRNA vaccine cardiac adverse event (CAE) in boys by age vs. COVID-19
hospitalization risk in the context of disease prevalence and presence of >1 comorbidity.
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1
Supplement 1: CDC working case definition for acute myocarditis
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2
Supplement 2: Study Profile
Supplement 3. Pediatric COVID-19 hospitalization rates by age and week in the United States
from COVID-NET [8].
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