Vaccines, Sera and Other Immunological Agents 441acid in stomach. However, if a large
number of bacteria are ingested, a
substantial number may reach the small
intestine. Symptoms include periodic fever,
headache, tiredness and weakness, changes
in behaviour and abdominal discomfort
with constipation in the early stages of the
disease followed by diarrhoea later.
Typhoid vaccines are used for active
immunisation against typhoid fever. Two
types of vaccine, one injectable and other
oral are available.
Polysaccharide Typhoid Vaccine
It is prepared from Vi capsular
polysaccharide of Salmonella typhi.
Immunity develops 7 to 15 days after
injection and protection lasts for three
years.
Adverse effects include slight local
pain, fever and rash.
It is indicated for prevention of typhoid
fever in adults and children over five years.
Dosage: Single dose of 0.5 ml SC or IM.Oral Typhoid Vaccine
It contains the attenuated strain Ty21a
of Salmonella typhi. The attenuation is due
to the absence of enzyme uridine
diphosphate galactose-4-epimerase which
is essential for the production of the
lipopolysaccharide ‘O’ antigen. The
absence of this enzyme makes Ty21a highly
immunogenic.
Adverse effects include fever and/or
mild GI effects.
It is indicated for prophylactic
immunization of adults and children over
six years against typhoid fever.
Dosage: One capsule on day 1, 3 & 5
irrespective of age and weight.HIB (H. INFLUENZAE TYPE B;
VAXIGRIP)
Haemophilus influenzae is a bacteria
which exists in many forms. The type B
form called Hib, commonly produces
disease in humans by colonizing the upper
respiratory tract of up to 80 percent of the
population and is major cause of infection
and mortality in children.
Almost all Hib disease occurs in
children younger than five years and
mostly in children younger than one year.
Transmission of Hib from one individual
to another primarily occurs via respiratory
secretions from carriers. However, Hib can
also be spread through direct contact with
a person with Hib disease but this accounts
for only two percent of cases in children
younger than four years old.
The manifestations of Hib disease are
varied with the most serious being
meningitis and epiglottitis.
Adverse effects include mild and
transient local erythema, swelling, fever,
irritability, sleepiness, GIT disturbances,
rashes and anorexia.
It is indicated for immunisation of
children against invasive disease caused by
Haemophilus influenzae type b (meningitis,
septicemia, cellulitis, arthritis, epiglottitis).
The safety and efficacy of Hib vaccines
have clearly been demonstrated in
developed countries and their introduction
into the national vaccination programme
of developing countries in the future can
markedly reduce the incidence of Hib-
related disease worldwide.