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P A R T 3
Drugs acting on the immune system
many cervical cancers. This vaccine is given in a series of
three injections to achieve full protection. In many cases,
antibody titres (levels of the antibody in the serum) can
be used to evaluate a person’s response to an immunisa-
tion and determine the need for a booster dose.
Due to recent events and the fear of terrorist activi-
ties, concern has risen about the use of various diseases
as biological weapons. Box 18.5 discusses vaccines and
the use of biological weapons.
Therapeutic actions and indications
Vaccines stimulate active immunity in people who are
at high risk for development of a particular disease. The
vaccine needed for a person depends on the exposure
that person will have to the pathogen. Exposure is
usually determined by where the person lives and their
travel plans, and work or family environment exposures.
Vaccines are thought to provide lifelong immunity to the
disease against which the individual is being immunised.
Table 18.1 lists the various vaccines available along with
usual indications.
Pharmacokinetics
There is no pharmacokinetic information on these bio-
logicals, which are treated like endogenous antibodies
in the body.
The events of September 11 2001 and the subsequent war
on terrorism have heightened awareness of several diseases
that might be in development as biological weapons.
Anthrax, plague, tularaemia, smallpox, botulism and a
variety of viral haemorrhagic fevers are all considered to be
likely biological warfare weapons.
Anthrax
An imported vaccine is available in Australia made from
inactivated cell-free filtrate of a virulent strain of the
anthrax bacillus. It is available only for military use. Active
production stopped in 1998, but production and supply
issues were made high priorities. Ciprofloxacin and, in
sensitive cases, doxycycline and penicillins are effective
in treating postexposure cases. The vaccine is given and
repeated in 2 and 4 weeks, along with the appropriate
antibiotic, to people who have been exposed.
Plague
Plague is easily spread from person to person, and without
treatment can progress rapidly to respiratory failure
and death. There is currently no vaccine for plague; a
whole-cell vaccine that was used for many years is no
longer available. Research is ongoing using a pneumonic
plague vaccine that has successfully protected animals.
Several drugs have been found to be life-saving with
plague—streptomycin, doxycycline, ciprofloxacin and
chloramphenicol.
Smallpox
Smallpox was considered eradicated since no new cases
had been seen in 20 years. Smallpox is highly transmissible
and has a 30% mortality rate in unvaccinated people.
Immunisation against smallpox ended in the 1970s.
There is now a commercially available vaccine, but use
is somewhat limited because of questions raised during
studies of the vaccine. It is given to military personnel and
people thought to be at high risk. It is currently thought
that the vaccine is no longer effective after 20 years,
although there is no definite evidence that previously
vaccinated people have no protection. The smallpox
vaccine uses live virus, placed in punctures made in the
skin. After exposure, vaccination given within the first
3 to 4 days can prevent the disease. If it has been 7 days or
longer since exposure, the vaccine and a vaccinia immune
globulin should be used, if any are available. So far no
drugs are thought to be effective in treating smallpox.
Early studies have, however, shown cidofovir (
Vistide
) to
be effective in vitro.
Tularaemia
Tularaemia in an aerosolised form can cause systemic
and respiratory illness with a 35% mortality rate. It is
not passed from person to person. There is no vaccine
available, but doxycycline and ciprofloxacin can be used
after exposure, and gentamicin has been effective after
symptoms appear.
Botulism
Botulism, produced by
Clostridium botulinum
, can be
aerosolised or used to contaminate food. The toxin it
produces causes cranial nerve palsies that can result in
muscle paralysis and respiratory failure. Antitoxin is also
available for people with specific exposures, and research
is ongoing with an equine antitoxin effective against
all seven serotypes of botulism that is thought to cause
fewer hypersensitivity reactions than what is currently
available.
Viral haemorrhagic fever
Lassa, Marburg, Junin and Ebola viruses cause
haemorrhagic fevers with mortality rates as high as 90%.
No vaccines are currently available for these agents,
although the United States Army has had success with
a vaccine for Junin. Ribavirin has been effective in
some cases of Lassa fever and has been effective orally
for postexposure prophylaxis. It is being studied for
effectiveness with these other viruses. Currently there is
no established treatment and this area is one of the highest
priorities for combating possible biological warfare.
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BOX 18.5
Vaccines and biological weapons
