The Advisory
Committee on Immunization Practices is expected to make recommendations
in June on whether Americans should be vaccinated against
smallpox, a disease that no longer exists on the planet.
The United States and the rest of the world have been comfortable
for more than two decades in the knowledge that the last case
of smallpox occurred in 1977, and the disease was declared
completely eradicated in 1980. After eliminating stocks of
the virus in laboratories worldwide, the World Health Organization
was able to say in 1984 that the only remaining variola virus
isolates are stored at just two sites: the Centers for Disease
Control and Prevention in Atlanta and the State Research Center
of Virology and Biotechnology in Novosibirsk, Russia.
But there are lingering concerns that the virus resides
outside those laboratories and could be used as a weapon by
terrorists. And the effects of such a terrorist attack would
be catastrophic, say public health officials, for two reasons:
the virus is highly contagious and spreads readily and rapidly
from person to person, and almost no one in the United States
is immune to the infection. Smallpox vaccination has not been
performed routinely in this country since 1972, so there is
now a large population of children and young adults who were
never immunized. And even persons born before 1972, who probably
received a smallpox vaccination in order to enter school and
have the scar to prove it, may no longer be immune, since
no one knows exactly how long vaccination-induced immunity
lasts.
That means almost everyone in the United States would potentially
be at risk if terrorists introduced the smallpox virus, either
by sending infected persons to mingle with crowds or by disseminating
the virus itself in the air or on commonly used objects. That
poses questions for the Committee on Immunization Practices,
including:
- Should we act now to make smallpox vaccine available to
everyone in the United States, or, alternatively, to young
people between the ages of one year and 29 who were never
vaccinated; and should vaccination be compulsory or voluntary?
- Or should we wait until there is an attack, relying on
the fact that immunization within two or three days of exposure
seems to prevent or lessen the severity of smallpox?
A number of factors may enter into the committee's decisions.
One is whether there is enough smallpox vaccine to carry through
whatever recommendation the committee may come up with. There
is currently a limited stockpile of vaccine in this country,
most of it produced in 1982 or earlier. In studies published
in April in the New England Journal of Medicine, researchers
reported that they found those vaccines can be diluted 5-
to 10-fold "without substantial loss of efficacy." "When administered
by a bifurcated needle to previously unvaccinated adults,
the vaccine produced vesicular skin lesions that correlate
with the induction of the antibody and T-cell responses that
are considered essential for clearing vaccinia virus infections."
That means, says Dr. Anthony Fauci of the National Institutes
of Allergy and Infectious Diseases, that "The current stockpile
of 15 million doses of smallpox vaccine may safely be diluted
to yield at least 75 million doses." In addition, he points
out, the ongoing production of second-generation smallpox
vaccines will increase our supply to approximately 286 million
doses by the end of this year, and the Department of Health
and Human Services has said it will test for safety and immunogenicity
some 75 million doses of vaccine that recently were discovered
to have been stored by a pharmaceutical company since 1972.
"Thus, the availability of vaccine will soon become less of
a factor in the formulation of a policy," Fauci said.
Another point the advisory committee may consider is how
immunization on a massive scale might be handled, either before
or during a terrorist attack. In its successful campaign to
eradicate smallpox worldwide 40 years ago, the World Health
Organization relied on a technique called "ring vaccination,"
which is the approach currently recommended in guidelines
developed by the Centers for Disease Control and Prevention.
In ring vaccination, patients with suspected or confirmed
smallpox are isolated; contacts are traced, vaccinated, and
kept under close surveillance; and high-risk persons who may
have had direct or indirect contact with the patient are identified
and vaccinated.
"Despite the fundamental soundness of this approach and
its success in previous naturally occurring outbreaks, there
is considerable skepticism about the feasibility of this strategy,"
in the event of a terrorist attack, Fauci notes, since multiple
exposures and the resulting panic could overwhelm the capacity
of CDC and local authorities to carry out the plan. And most
importantly, he points out, previous outbreaks that were controlled
by ring vaccination were in the context of existing herd immunity,
not in an essentially non-immune population.
But the factor that seems most likely to affect public opinion
about the need to vaccinate in advance of an attack, says
Dr. William Bicknell of the Boston University School of Public
Health, is that smallpox vaccination often has adverse reactions
in otherwise healthy persons. Commonly, researchers reported,
the healthy young volunteers who received either full-strength
or dilute vaccine to test its efficacy experienced side effects
including the formation of satellite lesions, regional lymphadenopathy,
fever, headache, nausea, muscle aches, fatigue, and chills,
as well as generalized and local rashes.
 |
... "There's no other vaccine that we currently give that carries with it a risk of death."
-- Alex Kemper
|
In studies reported to the Pediatric Academic Societies
annual meeting in Baltimore, Maryland, May 7, pediatricians
Alex Kemper and Matthew Davis of the University of Michigan
predicted that a mass campaign to vaccinate Americans against
smallpox could result in 200 to 300 deaths and might make
several thousand people severely ill with complications such
as viral infection spreading from the vaccination site and
severe skin rashes. "There's no other vaccine that we currently
give that carries with it a risk of death," Kemper pointed
out. "From a societal viewpoint, we have to decide whether
or not we're willing to take this risk."
But in making its recommendations, the advisory committee
is expected to weigh the very serious nature of smallpox itself
against the possibility of adverse reactions to immunization
in a limited number of people. Most doctors and nurses now
in practice have never seen a case of smallpox, but a doctor
who treated 22 smallpox patients while stationed with the
military in Japan in 1945 described the experience in a New
England Journal of Medicine article. "The disease began
with a high fever," Dr. Murray Dworetzky recalled, "with the
temperature exceeding 40 degrees Centigrade and then dropping,
although never to normal, before it spiked again. Although
some patients had pustular lesions, those who died had confluent
subcutaneous hemorrhages that rapidly involved the entire
body, with a similar enanthema involving the mucous membrances
of the oral cavity, respiratory mucosa, and entire gastrointestinal
tract. The pain was intense and morphine relieved it only
marginally." Fourteen of the 22 patients died.
Another New England Journal article notes that the
incubation period for the disease is 7 to 17 days, after which
severe backache, headache, and fever begin abruptly. Lesions
occur first on the face and extremities but then cover the
entire body. After severe smallpox, pockmarks or pitted lesions
are seen in 65 to 80 percent of survivors, most commonly on
the face. Death from smallpox is ascribed to toxemia, associated
with immune complexes, and to hypotension.
In any case, the New England Journal of Medicine
editorializes, "The debate on preemptive vaccination cannot
go on indefinitely. We need to make a decision. If we do proceed
with large-scale vaccination, we need to consider what operational
plans might be workable, who should be immunized, when they
should be immunized, and how to reduce unintended sequelae."
The complete text of the New England Journal of Medicine's
discussion of smallpox and bioterrorism is available at http://content.nejm.org/content/vol346/issue17/index.shtml?query=TOC
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