-
Myopericarditis
following
smallpox
vaccination
among vaccinia-naive
US military
personnel.
Halsell
JS,
The University
of Virginia,
Charlottesville,
USA.
CONTEXT: In the
United States,
the annual
incidence of
myocarditis is
estimated at 1
to 10 per
100,000
population. As
many as 1% to 5%
of patients with
acute viral
infections
involve the
myocardium.
Although many
viruses have
been reported to
cause
myopericarditis,
it has been a
rare or
unrecognized
event after
vaccination with
the currently
used strain of
vaccinia virus
(New York City
Board of
Health).
OBJECTIVE: To
describe a
series of
probable cases
of
myopericarditis
following
smallpox
vaccination
among US
military service
members reported
since the
reintroduction
of vaccinia
vaccine. DESIGN,
SETTING,
PARTICIPANTS:
Surveillance
case definitions
are presented.
The cases were
identified
either through
sentinel
reporting to US
military
headquarters
surveillance
using the
Defense Medical
Surveillance
System or
reports to the
Vaccine Adverse
Event Reporting
System using
International
Classification
of Diseases,
Ninth Revision.
The cases
occurred among
individuals
vaccinated from
mid-December
2002 to March
14, 2003. MAIN
OUTCOME MEASURE:
Elevated serum
levels of
creatine kinase
(MB isoenzyme),
troponin I, and
troponin T,
usually in the
presence of
ST-segment
elevation on
electrocardiogram
and wall motion
abnormalities on
echocardiogram.
RESULTS: Among
230,734 primary
vaccinees, 18
cases of
probable
myopericarditis
after smallpox
vaccination were
reported (an
incidence of 7.8
per 100,000 over
30 days). No
cases of
myopericarditis
following
smallpox
vaccination were
reported among
95,622 vaccinees
who were
previously
vaccinated. All
cases were white
men aged 21
years to 33
years (mean age,
26.5 years), who
presented with
acute
myopericarditis
7 to 19 days
following
vaccination. A
causal
relationship is
supported by the
close temporal
clustering (7-19
days; mean, 10.5
days following
vaccination),
wide geographic
and temporal
distribution,
occurrence in
only primary
vaccinees, and
lack of evidence
for alternative
etiologies or
other diseases
associated with
myopericarditis.
Additional
supporting
evidence is the
observation that
the observed
rate of
myopericarditis
among primary
vaccinees is
3.6-fold (95%
confidence
interval,
3.33-4.11)
higher than the
expected rate
among personnel
who were not
vaccinated. The
background
incidence of
myopericarditis
did not show
statistical
significance
when stratified
by age (20-34
years: 2.18
expected cases
per 100,000; 95%
confidence
interval [CI],
1.90-2.34), race
(whites: 1.82
per 100,000; 95%
CI, 1.50-2.01),
and sex (males:
2.28 per
100,000; 95% CI,
2.04-2.54).
CONCLUSION:
Among US
military
personnel
vaccinated
against
smallpox,
myopericarditis
occurred at a
rate of 1 per 12
819 primary
vaccinees.
Myopericarditis
should be
considered an
expected adverse
event associated
with smallpox
vaccination.
Clinicians
should consider
myopericarditis
in the
differential
diagnosis of
patients
presenting with
chest pain 4 to
30 days
following
smallpox
vaccination and
be aware of the
implications as
well as the need
to report this
potential
adverse advent.
