Immunization against these three unrelated diseases is considered together because the vaccines are non-living and are often co-administered as a triple vaccine as part of the childhood vaccination programme.
DIPHTHERIA, TETANUS AND A CELLULAR PERTUSSIS (DTAP) IMMUNIZATION
Immunization against these three unrelated diseases is considered together
because the vaccines are non-living and are often co-administered as a triple
vaccine as part of the childhood vaccination programme.
This is an acute, non-invasive infectious disease associated with the
upper respiratory tract . The incubation period is 2-5 days although the
disease remains communicable for up to 4 weeks. A low molecular weight toxin is
produced which affects the myocardium, nervous and adrenal tissues. Death
results in 3-5% of infected children. Diphtheria immunization stimulates the
production of an antitoxin which protects against the disease but not against
infection/colonization of the respiratory tract. The immunogen is a toxoid,
prepared by formaldehyde treatment of the purified toxin and administered while
adsorbed to an adjuvant, usually aluminium phosphate or aluminium hydroxide.
The primary course of diphtheria prophylaxis consists of three doses starting
at 2 months of age and separated by an interval of at least 1 month. The immune
status of adults may be determined by administration of Schick test toxin, which
is essentially a diluted form of the vaccine.
Tetanus results from the production of a toxin by germinating spores and
vegetative cells of Clostridium tetani that can potentially infect deep wounds.
The organism, which may be introduced into the wound, grows anaerobically at
such sites. The toxin is adsorbed into nerve cells and has a profound effect on
nerve synapses resulting in spastic paralysis in affected individuals.
Mortality rates are highest in individuals over 60 years of age and the
unvaccinated. Tetanus immunization employs a toxoid and protects by stimulating
the production of antitoxin. This antitoxin will neutralize the toxin as the organisms
release it and before it can be adsorbed into nerves. As the toxin is produced
only slowly after infection, the vaccine, which acts rapidly, may be used
prophylactically in non-immunized individuals who have recently suffered a
high-risk injury. The toxoid, as with diphtheria toxoid, is formed by reaction
with formaldehyde and is adsorbed onto an inorganic adjuvant. The primary
course of tetanus vaccination consists of three doses starting at 2 months of
age and is separated by an interval of at least 1 month.
Whooping cough is caused by the non-invasive respiratory pathogen
Bordetella pertussis. This disease may be complicated by broncho-pneumonia, or
by repeated posttussis vomiting leading to weight loss and to cerebral hypoxia
associated with a risk of brain damage. Until the mid 1970s the mortality from
whooping cough was about 1 per 1000 notified cases, with a higher rate for
infants under 1 year of age. A full course of vaccine now consists of highly
purified selected components of the Bordetella pertussis organism (i.e.
acellular pertussis) which are treated with formaldehyde or glutaraldehyde and
absorbed on to aluminium phosphate or aluminium hydroxide adjuvants. This
vaccine gives considerably lower incidence of local and systemic reactions in
comparison to the whole-cell pertussis vaccine that preceded it and gives
comparable protection (> 80%). The primary course of pertussis prophylaxis
consists of three doses starting at 2 months of age and separated by an
interval of at least 1 month.
The primary course of DTaP protection consists of three doses of a
combined vaccine, each dose separated by at least 1 month and commencing not
earlier than 2 months of age. In such combinations, the pertussis component of
the vaccine acts as an additional adjuvant for the toxoid elements. Tetanus and
diphtheria vaccines are also available in a combined
tetanus/diphtheria/inactivated polio vaccine (Td/IPV) vaccine.
The primary course of pertussis vaccination is considered sufficient to
confer lifelong protection, especially as the mortality associated with disease
declines markedly after infancy. The risks associated with tetanus and
diphtheria infection however persist throughout life. The Td/IPV vaccination is
therefore repeated before school entry, at 4-5 years of age, and once again at
puberty.
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