HIB VACCINE : Why it should be included in the immunisation schedule?
Dr. Rohit C. Agarwal
Hon. Secretary General, IAP; Consultant Pediatrician, Hira Nandani Hospital, Mumbai
Haemophilus influenzae type B, or Hib, is a bacterium estimated
to be responsible for some three million serious illnesses and an
estimated 386,000 deaths per year, chiefly through meningitis
and pneumonia. Almost all victims are children under the age of
five, with those between four and 18 months of age especially
vulnerable. In developing countries, where the vast majority of Hib
deaths occur, pneumonia accounts for a larger number of deaths
than meningitis. However, Hib meningitis is also a serious problem
in such countries with mortality rates several times higher than
seen in developed countries; it leaves 15 to 35% of survivors with
permanent disabilities such as mental retardation or deafness.
Contrary to what the name Haemophilus influenzae suggests, the
bacterium does not cause influenza.
Hib is commonly found in the noses and throats of healthy
individuals living in regions where vaccination is not carried out.
Almost all unvaccinated children are exposed to Hib by age five.
The bacterium is spread by exhaled droplets. Occasionally, Hib
can invade the bloodstream and cause infection and disease
in other parts of the body, including the meninges leading to
meningitis, and the lungs, causing pneumonia. Unlike measles,
polio or diphtheria, Hib does not cause a specific illness with
which it, alone, can be identified. The most deadly forms of Hib
infection include pneumonia and meningitis, but those diseases
can have other causes, and can look the same whether caused by
Hib or some other agent. More rarely, Hib is responsible for other
life-threatening complications in young children, such as septic
arthritis, an inflammation of the joints, and septicaemia, both of
which also can have other causes. And it may lead to epiglottitis.
Hib is preventable - highly effective vaccines have been available
since the early 1990s. Yet hundreds of thousands of children die year
after year from Hib disease. The two major obstacles to prevention
of Hib disease are a shortage of information and a shortage of
money. The information shortage is largely due to the difficulty of
diagnosing Hib disease - it claims most of its victims without ever
being recognized. In addition, Hib vaccine is more expensive than
classic childhood vaccines - at the price offered to the world’s lower
income nations in 2005, it costs roughly seven times the total cost
of vaccines against measles, polio, tuberculosis, diphtheria, tetanus,
and pertussis. Those two factors put many developing countries in
a difficult situation. They want evidence of the extent and damage
done by Hib before deciding whether to add a more costly vaccine
to their infant immunization programmes. Developing countries
may also need external funding assistance if they decide to provide
vaccination against Hib.
89 countries offered infant immunization against Hib by the
end of 2004, with two of those countries providing it in parts of
their territories. 92% of the populations of developed countries
was vaccinated against Hib as of 2003. The vaccination coverage
was 42% for developing countries, and 8% for least-developed
countries. Hib conjugate vaccines, given by intramuscular
injection, are highly effective and have almost no side effects.
Three doses are usually administered in infancy, starting at around
age six weeks. In some countries, a booster dose is also offered
between 12 & 18 months of age. The Global Immunization Vision
and Strategy (GIVS), developed by WHO, UNICEF, and partners, has
among its aims “strengthening the current immunization system
so that it can maximally deliver currently available vaccines as well
as under-utilized vaccines,” including Hib.