Hong Kong Med J 2021 Oct;27(5):326–7 | Epub 16 Aug 2021
© Hong Kong Academy of Medicine. CC BY-NC-ND 4.0
EDITORIAL
mRNA COVID vaccine and myocarditis in
adolescents
Mike YW Kwan, MSc (Applied Epidemiology) (CUHK), FHKAM (Paediatrics)1 #; Gilbert T Chua, MB, BS, FHKAM (Paediatrics)2 #; CB Chow, MD, FHKAM (Paediatrics)1,2 #; Sabrina SL Tsao, MB, BS(UK), FACC2; Kelvin KW To, MD, FRCPath3; KY Yuen, MD, FRCPath3; YL Lau, MD (Hon), FRCPCH2; Patrick Ip, MPH, FHKAM (Paediatrics)2
1 Department of Paediatrics and Adolescent Medicine, Princess Margaret Hospital, Hong Kong
2 Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
3 Department of Microbiology, Carol Yu Centre for Infection, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
# These authors contributed equally to the work.
Corresponding authors: Prof KY Yuen (kyyuen@hku.hk), Prof YL Lau (lauylung@hku.hk), Dr Patrick Ip (patricip@hku.hk)
In Hong Kong, the coronavirus disease 2019
(COVID-19) vaccination programme started on
26 February 2021. CoronaVac (an inactivated virus
vaccine developed by Sinovac) and Comirnaty
(BNT162b2 mRNA vaccine co-developed by
BioNTech and Pfizer, and manufactured and
distributed in China by Fosun Pharma) are the
available formulations for public use. Comirnaty is
safe and provides good antibody response, including
for patients aged 12 to 15 years with
clinical efficacy in protecting against severe acute
respiratory syndrome coronavirus 2 (SARS-CoV-2)
infection of 100%.1 On 14 June 2021, the Food
and Health Bureau, Hong Kong SAR Government
lowered the age limit for receiving the Comirnaty
vaccine to ≥12 years.2
Since April 2021, there have been reports that
myocarditis and pericarditis occur more frequently
in adolescents and young adults after mRNA
COVID-19 vaccinations internationally.3 4 5 In Hong
Kong, Comirnaty is the only mRNA technology
platform COVID-19 vaccine available, but others are
available elsewhere (eg, from Moderna).
Myocarditis and pericarditis have many
virological and immunological causes, and are
known to occur after vaccination; for example, the
incidence of myocarditis after smallpox vaccination
is around 12 to 16.1 per million vaccinated individuals.6
Myocarditis can also occur after SARS-CoV-2
infection alone or as a consequence of multisystem
inflammatory syndrome in children after COVID-19
or paediatric inflammatory multisystem syndrome
temporally associated with SARS-CoV-2.3 7 8
Reported cases of myocarditis after mRNA
COVID-19 vaccination are mostly male adolescents
and young adults aged between 12 and 24 years who
received the second dose of the mRNA vaccine.9 10 11 12 13 14
These heart complications are exceedingly rare, but
are increasingly reported as hundreds of million
doses of mRNA COVID-19 vaccines have been
administered worldwide.4 5 9 10 The typical symptoms
of myocarditis and pericarditis are chest pain,
shortness of breath, and palpitations occurring within 1 week (usually 2-4 days) after vaccination.
The condition is mild in most of the affected
individuals, with only minimal treatment required
and full recovery within a few days.
Although myocarditis and pericarditis have
many virological and immunological causes, a
causal link was suspected due to the immunological
reaction to the mRNA COVID-19 vaccine.
Individuals are recommended to rest and refrain
from heavy strenuous activities for 1 week after
mRNA COVID-19 vaccination, which will be
helpful during the rare occurrence of myocarditis
or pericarditis. Individuals experiencing chest pain,
shortness of breath, or palpitations after receiving
the mRNA vaccine are advised to seek immediate
medical attention.
Myocarditis and pericarditis are diagnosed
according to the Brighton Collaboration case
definitions,11 which include clinical symptoms
(cardiac or non-specific symptoms), elevated
myocardial biomarkers (troponin T, troponin I,
or CK myocardial band), electrocardiographic,
echocardiogram or cardiac magnetic resonance
abnormalities and with other alternative aetiologies
for symptoms excluded.12 Supportive therapy is the
mainstay of treatment with cardiac treatment and
intervention if needed. Individuals with myocarditis/pericarditis are advised to rest until symptoms
resolved.12
Based on the latest scientific data, the benefits
of COVID-19 vaccination to the individual, family
members, and society outweigh the reported
known and potential risks of vaccination (including
the possibility of myocarditis and pericarditis)
in the current pandemic.13 Owing to the recent
emergence of SARS-CoV-2 variants with increased
transmissibility, higher rates of vaccination will
be required to achieve sufficient herd immunity
to prevent further community spread and allow society to return to normal.
On 30 June 2021, a joint consensus statement
was issued by the Hong Kong Paediatric Society,
The Hong Kong Society for Paediatric Immunology Allergy and Infectious Diseases, the Hong Kong
College of Paediatric Nursing, and the Hong Kong
Paediatric Nurses Association.14 The consensus
statement appeals to children and adolescents (aged
≥12 years), parents, adult household members, and
child-carers to receive the COVID-19 vaccine for
self-protection, and for the physical health and long-term
psychosocial development of all children in
Hong Kong.
The Centers for Disease Control and
Prevention and the Food and Health Bureau of
Hong Kong SAR Government endorse the use of
Comirnaty vaccine in adolescents mainly because
the benefits of vaccination exceed the risks of
SARS-CoV-2 infection.15 Although there is no
alternative vaccine for this age-group currently
available, data are being gathered on CoronaVac,
which utilises the inactivated virus platform.
If this proves safe and effective for children and
adolescents, and is approved for use, CoronaVac may
be an alternative for this age-group in Hong Kong.
Author contributions
All authors contributed to the concept or design of the study,
acquisition of the data, analysis or interpretation of the
data, drafting of the manuscript, and critical revision of the
manuscript for important intellectual content. All authors
had full access to the data, contributed to the study, approved
the final version for publication, and take responsibility for its
accuracy and integrity.
Conflicts of interest
All authors have disclosed no conflicts of interest.
References
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