       
Study Urges Mass Inoculation Against Smallpox
MONDAY, July 8 (HealthScoutNews) -- The government's vaccination
strategy to combat a smallpox attack by containment would likely
cost thousands more lives more than a wider inoculation effort,
according to a new analysis.
The smallpox vaccine is highly effective against the virus, but
in a small percentage of people it can cause serious and potentially
fatal side effects.
Health officials therefore believe that the risks of a mass
immunization campaign outweigh the odds of a bioterrorism attack
with smallpox -- at least so far. Instead, the Centers for Disease
Control and Prevention has advocated a policy of "ring vaccination"
and quarantines to contain the deadly virus, which the World Health
Organization declared eradicated in 1980.
In this strategy, smallpox vaccine is given as needed to
successively wider circles of people who've come into contact with
the infection. Only if this approach fails to stem the outbreak
would the government proceed with a mass inoculation plan.
However, the three disease modelers -- Edward Kaplan of Yale
University and Lawrence Wein and David Craft of the Massachusetts
Institute of Technology -- found that in a hypothetical attack on a
city with 10 million inhabitants, mass inoculation is the best
strategy for reducing deaths.
Last month, an advisory panel for the CDC recommended immunizing
roughly 15,000 emergency workers, hospital staff and other "first
responders" likely to encounter the disease early in an attack.
Officials now believe that number may ultimately reach 500,000, and
the government is making plans for a massive public vaccination
effort if needed.
Kaplan, Wein and Craft, who report their calculations this week
in the Proceedings of the National Academy of Sciences,
assume 1,000 people are initially infected in the attack. If so,
ring vaccination followed by mass vaccination four weeks later would
lead to about 4,100 more deaths than if mass immunizations occurred
at the first signs of disease, they said. Mass vaccination would
also trim the life span of the outbreak substantially.
The researchers offered two reasons for the difference. Finding
contacts of infected people takes precious time, allowing others to
become infected and fall ill before they can receive the
inoculation. And in dealing with this congestion, "queues" pile up,
further sapping the time-sensitive powers of the vaccine.
The researchers said their computer simulations showed
vaccinating 40 percent of the city's residents before an
attack would prevent nearly 40,000 deaths compared with a targeted
inoculation program.
In the absence of a pre-attack immunization, the researchers
argue that "serious consideration" be given to swapping the CDC's
current policy of ring vaccination for the mass vaccination plan
they modeled.
Dr. Craig Smith, a smallpox expert in Georgia and a member of the
Infectious Disease Society of America's bioterrorism work group,
said mass vaccinations and ring vaccinations are complementary, not
mutually exclusive. "There's huge overlap" between the two
approaches, said Smith, who was familiar with the computer model
offered by Wein, Craft and Kaplan.
"The crux comes down to whatever you think the risk of an attack
will be," said Smith, whose group advised the CDC panel. "We're
trying to make a decision on a disease that no longer exists outside
of a test tube. That's why you hear all the tap dancing."
Officials at the U.S. Department of Health and Human Services,
CDC's parent agency, did not return calls for comment Monday.
What To Do
For more on biological terrorism, visit the
Center for Civilian
Biodefense Strategies at Johns Hopkins University or the
Sabin Vaccine Institute.
To learn about the various bioterror weapons, try the
American Medical Association.
|
