Smallpox
Vaccination in Massachusetts
Some responses
from the Massachusetts Department of Public Health to recent questions
related to smallpox preparedness by Alfred DeMaria, Jr., M.D., Director
of the Bureau of Communicable Disease Control and State Epidemiologist.
Does
the end of the Iraq War and the Saddam Hussein regime in Iraq mean the
end of the threat of smallpox and the imperative to plan for the potential
of smallpox as a bioterrorism threat?
No.
While there was some concern that Iraq had smallpox virus and could
release it, the threat of possible smallpox virus possession was never
limited to the former Iraqi regime. Plans for smallpox preparedness
were developed and completed through the work of the Smallpox Work Group
of the Massachusetts Department of Public Health Bioterrorism Preparedness
and Response Program Advisory Committee in the summer of 2002, before
concrete discussion of war in Iraq and before the President enunciated
his ultimatums to Iraq that led to war or announced the federal smallpox
plan in December of 2002. Thus, the Massachusetts smallpox plan was
developed without reference to Iraq or the war in Iraq and the program
was initiated without urgency related to the war. The situation remains
that we have no way to assess the risk of smallpox as a bioterrorist
weapon. The Massachusetts plan is based on the assumption that some
small, but real, threat exists and a minimal number of individuals among
several professional disciplines need to be vaccinated to be able to
respond to smallpox without significant risk to their lives.
Is
there a significant risk of injury and death from smallpox vaccination?
Smallpox
vaccine does have serious adverse events associated with its use. These
must be and have been taken seriously. However, objectively and quantitatively
the risk of smallpox vaccination is low, especially in previously vaccinated
adults who are carefully screened for risk factors for adverse events.
Data from the 1960s have been used to guide risk assessment, but these
data have limitations that under-estimate some risks, as demonstrated
by the new appreciation of the risk of myocarditis and myopericarditis
generated by the military and civilian vaccination programs, but over-estimate
others. Another limitation of historical data occurs when all vaccinees
are aggregated. When analyzed by excluding people being screened out
of the current program, the rates of adverse events are two to four-fold
lower than the overall rates. Most of the possible myocarditis cases
being observed in current programs are in the previously unvaccinated.
Rates of adverse events in all studies are low; serious adverse events
in the range of less than 100 per thousand, conservatively assessed,
or 0.01%, 1 per 10,000. Now we have the accrued, modern experience of
the U.S. military and civilian programs. In the military program, with
over 450,000 vaccinated, with most vaccinees (70.5%) being not previously
vaccinated, there were 38 moderate or severe adverse events (0.008%)
and 106 mild or temporary events (0.02%), with no deaths, cases of eczema
vaccinatum or progressive vaccinia. All adverse events resolved and
only 0.5-3.0% of vaccinees required any sick leave. Among 37,800 civilian
vaccinees, there were 71 serious adverse events of any sort following
vaccination (0.2%), which may or may not have been related to vaccination.
Myopericarditis has become the most frequent serious adverse event,
but almost all who develop myopericarditis recover without apparent
sequelae. The relationship of other cardiac events with vaccination
is unclear. All volunteers are now screened for history of cardiac disease
and risk factors before being vaccinated.
Does
vaccinating health care workers put patients in danger?
Although
we must be concerned for transmission of vaccinia virus to patients,
especially immune compromised patients, this remains a theoretical risk.
The vaccination program provides extensive infection control instruction
and a detailed protocol for handling site and dressing, health care
workers use impermeable dressings that contain virus and dressings are
inspected prior to each shift. There have been no transmissions of vaccine
virus from vaccinated health care workers to patients in the experience
of vaccinating civilian health care workers in hospitals or at the National
Institutes of Health, in the Israeli experience vaccinating over 14,000
health care workers and in the U.S. military experience amounting to
more than 19,000 worker-months of clinical contact.
Haven’t
public health agencies lost interest in smallpox preparedness involving
vaccination?
No.
The rationale for smallpox vaccination in preparation for the threat
of smallpox release as a terrorist act has not changed. In order to
be able to ask health care workers and others to respond to smallpox,
we need to vaccinate them first. Smallpox is associated with a 50% mortality
rate in the never vaccinated. The Massachusetts plan was not implemented
with a sense of urgency, but there has been and continues to be determination
to achieve the goal of having a sufficient number of professionals from
multiple disciplines who can be called upon to respond to smallpox without
fear of acquiring the infection.
Doesn’t
vaccination within 4 days of exposure to smallpox prevent smallpox?
No.
Although some people vaccinated after smallpox exposure will escape
getting smallpox (as will some people who are not vaccinated), most
people vaccinated after smallpox exposure will still get smallpox, although
they are very likely to get a milder case and are much less likely to
die from smallpox. Persons exposed to smallpox will have to be quarantined
or be subject to personal surveillance for the time they may develop
smallpox, despite being vaccinated. Persons exposed to smallpox who
are vaccinated, but do not have a take, will likely get an unmitigated
case of smallpox. Therefore, a response plan that involves vaccination
only after exposure will not prevent smallpox, will not avoid the need
to quarantine the exposed (and therefore restrict their work and contacts),
and, in the small proportion of people who do not have a successful
vaccination, will lead to severe and life-threatening disease. On the
other hand, there has never been a case of smallpox reported in a smallpox
care-giving health care worker who had been vaccinated within seven
years of providing that care. Post-exposure vaccination is a critical,
life-saving component of disease control in the event of smallpox release,
but is not sufficient preparation for responders to smallpox.
Can’t
unvaccinated health care workers rely on patient isolation and personal
protective equipment to protect them from smallpox?
No.
Isolation and personal protective equipment are critical to the management
of smallpox cases, but may not be sufficient to provide adequate protection
for the unvaccinated. There has been no experience in using personal
protective equipment in the absence of vaccination as part of prevention
of transmission of smallpox. Studies of infection control for smallpox
were performed in an era in which the vast majority of people involved
in care had been vaccinated and had been exposed to vaccinia virus (an
in many cases smallpox) on many occasions (leading to boosting of immunity)
and before the modern era of infection control practice. The only airborne
infection that has been adequately studied in respect to using personal
protective equipment is tuberculosis, and tuberculosis is not as communicable
as smallpox and is not transmitted by contact. The current official
infection control recommendation is that everyone providing care for
cases of smallpox be vaccinated and use isolation and personal protective
equipment. Measles and chickenpox, to a degree, are transmitted in the
same fashion as smallpox, but health care workers who are susceptible
to these viral infections are generally not allowed to care for patients
with measles or chickenpox despite personal protective equipment, unless
it is unavoidable.
If
someone volunteers for smallpox vaccination, will they be forced to
work wherever they are sent, including possibly to another hospital
or health care facility, anywhere in the state?
No.
Participation in the vaccination and response program is entirely voluntary.
However, the purpose of the program is to have people available to respond
to smallpox who are immune to smallpox. Health care and other responders
are not being vaccinated because they might be exposed to smallpox (this
could happen to anyone should smallpox virus be released), but rather
are being vaccinated so that they can be asked to respond to smallpox,
should it occur. It is most likely that people will be asked to respond
to smallpox within their own professional scope of work and practice,
within their own work setting, especially if the goal of having a sufficient
number of vaccinated smallpox responders is achieved. However, there
is the possibility that people might be asked to respond to smallpox
in a setting other than their own usual work setting. This must obviously
be voluntary and the cooperation of employers will be necessary, as
well.
It should be understood that the existence or transmission of smallpox
in the United States would be an event of enormous threat and significance,
which would result in significant restrictions in travel and normal
activities, and is likely to result in suspension of schools, public
events and some businesses. Under those circumstances, many civilians
will be called upon to provide the assistance necessary to assure the
control of smallpox and vaccinated individuals may be needed to go beyond
their usual work setting. If the possibility that you might be asked
to make such a commitment in extraordinary, emergency circumstances
makes you uncomfortable, then you should not volunteer for smallpox
preparedness vaccination.
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