by Ben Tang

Created on: March 16, 2009

"Invasive infections such as pneumonia, meningitis, epiglottitis, septic arthritis, cellulitis, otitis media, pericarditis, endocarditis, and osteomyelitis"- is caused by the bacteria Haemophilus influenzae type b or in short Hib.

Children are most susceptible to this infection because most adults are usually immune to this bacteria due to natural immunity gained in childhood. Fatality due to this invasive infection is as high as 6% and up to 20% of surviving patients have permanent hearing loss. Fortunately, this disease is preventable through vaccination.

DEVELOPMENT HISTORY OF HIB

The first Hib vaccine licensed was a polysaccharide vaccine, first marketed in the US in 1985. It was found to be not effective in children younger than 18 months therefore limiting the usefulness of the vaccine, thus leading to market withdrawal in 1988.

Conjugate Vaccine

Subsequently, conjugate vaccine was produced. This vaccine combines the polysaccharide part with protein. This strategy greatly increased the ability to create successful immunity for young children. There are currently three types of conjugate vaccine utilizing different proteins in the conjugation process, all of which are highly effective: mutant diphtheria protein, tetanospasmin and meningococcal group B outer membrane protein.

Combination vaccines

Combination vaccines are newer vaccines that combine Hib vaccine with other vaccines which aims to reduce the need for multiple shots, improve compliance and ease of administration. The common combination is Hib vaccine with diphtheria-tetanus-pertussis-polio vaccines which is also refered to as pentavalent vaccine. Example of combination vaccine available in the US
is Infanrix Hib manufactured by Glaxo Smithkline

EFFICACY OF VACCINE

The Hib vaccine is only effective to prevent infection caused specifically by type B Haemophilus influenzae and not non-type B which is more rare than type B. Clinical efficacy among fully vaccinated children is estimated to be between 95-100%. This means that only a very small; less than 5% percentage of vaccinated children will be susceptible to the bacteria.

VACCINE SAFETY

Clinical trials and ongoing surveillance have proven that Hib vaccine to be safe. Side effects due to the vaccine are generally mild and self limiting. The most common reactions are gradual redness, swelling, or pain at the site of injection. More severe reactions are extremely rare, however if the breathing is affected, immediate medical attention should be seeked.

WHO SHOULD NOT RECEIVE THIS VACCINE?

Children younger than six weeks of age should not get Hib vaccine because a dose given at this time may not provide immunity. Anyone who has ever had a life-threatening allergic reaction to a previous dose of Hib vaccine should not get another dose. Persons with a moderate or severe acute illness should postpone receiving the vaccine until their condition has improved.

CAN THE VACCINE CAUSE HIB DISEASE?

No. Hib vaccine is a fractional vaccine therefore, it contains only part of the Hib microbe.

The Centers for Disease Control and Prevention (CDC) has recommended the use of the Hib vaccine since 1980 and due to the routine use of the Hib vaccine in the U.S. from 1980 to 1990, the incidence of invasive Hib disease has decreased from 40-100 per 100,000 children down to 1.3 per 100,000. This remarkable reduction is due to successful implementation of the Hib vaccination campaign.

Reference:

http://www.cdc.gov/doc.do/id/0900 f3ec8027b640

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