Hib vaccine

Haemophilus influenzae type b vaccine (Hib vaccine or PRP vaccine [cite journal
title=Haemophilus influenzae Type b Conjugate Vaccine (Meningicoccal Protein Conjugate): Immunogenicity and Safety at Various Doses
url=http://pediatrics.aappublications.org/cgi/reprint/85/4/690
format=PDF ("fee required")
first=Ram|last=Yogev
coauthors=Arditi, Moshe; Chadwick, Ellen Gould; et al.
date=1990-04-04
accessdate=2008-10-03
journal=Pediatrics
volume=85|issue=4|pages=690-693
pmid=2107520] ) is a conjugate vaccine developed for the prevention of invasive disease caused by Haemophilus influenzae type b bacteria. The Centers for Disease Control and Prevention (CDC) has recommended the use of the Hib vaccine. [cite journal
title=Recommendation of the Immunization Practices Advisory Committee (ACIP) Polysaccharide Vaccine for Prevention of Haemophilus influenzae Type b Disease
url=http://www.cdc.gov/mmwr/preview/mmwrhtml/00022818.htm
date=1985-04-19
accessdate=2008-10-03
journal=MMWR Weekly
volume=34|issue=15|pages=201-5
issn=0149-2195] Due to 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. [cite web
title="Haemophilus influenzae" Serotype b (Hib) Disease
url=http://www.cdc.gov/ncidod/dbmd/diseaseinfo/haeminfluserob_t.htm
date=2008-04-04
accessdate=2008-10-03
work=Disease Listing
publisher=Centers for Disease Control and Prevention] Vaccinations against "Haemophilus influenzae" (Hib) have decreased early childhood meningitis significantly in developed countries and recently in developing countries. [cite press release
title=Deadly Disease Eliminated in Children under Five Years of Age in Uganda
url=http://www.gavialliance.org/media_centre/press_releases/2008_03_10_uganda.php
date=2008-03-10
accessdate=2008-10-03
publisher=GAVI Alliance]

History and vaccine composition

Polysaccharide vaccine

The first Hib vaccine licensed was a pure polysaccharide vaccine, first marketed in the US in 1985.cite book
title=Epidemiology and Prevention of Vaccine-Preventable Diseases
author=Centers for Disease Control and Prevention
editor=Atkinson W, Hamborsky J, McIntyre L, Wolfe S
edition=9th ed.
publisher=Public Health Foundation
location=Washington, D.C.
year=2006] Similar to other polysaccharide vaccines, immune response to the vaccine was highly age dependent. It was found to be ineffective in childrenyounger than 18 months and was of variable effectiveness in older children. As a result, the age group with the highest incidence of Hib disease was unprotected, limiting the usefulness of the vaccine. The vaccine was withdrawn from the market in 1988.

Conjugate vaccine

The shortcomings of the polysaccharide vaccine lead to the production of the Hib polysaccharide-protein conjugate vaccine. Attaching Hib polysaccharide to a protein carrier greatly increased the ability of the immune system of young children to recognize the polysaccharide and develop immunity. There are currently three types of conjugate vaccine utilizing different proteins in the conjugation process, all of which are highly effective: tetanospasmin, mutant diphtheria protein, and meningococcal group B outer membrane protein.

Combination vaccines

Multiple combinations of Hib and other vaccines have been licensed in the United States, reducing the number of shots necessary to vaccinate a child. Hib vaccine combined with diphtheria-tetanus-pertussis-polio vaccines and Hepatitis B vaccines are available in the US. The World Health Organization (WHO) has certified several Hib vaccine combinations, including a pentavalent diphtheria-pertussis-tetanus-hepatitis B-Hib, for use in developing countries.

Efficacy

Hib conjugate vaccines have been shown to be universally effective against all manifestations of Hib disease, with a clinical efficacy among fully vaccinated children estimated to be between 95-100%. The vaccine has also been shown to be immunogenic in patients who are at high risk of invasive disease. Hib vaccine is not effective against non-type B "Haemophilus influenzae". However, non-type B disease is rare in comparison to pre-vaccine "Haemophilus influenzae" type B disease.

Safety

Clinical trials and ongoing surveillance have shown Hib vaccine to be safe. Adverse reactions to the vaccine are generally mild. The most common reactions are transient redness, swelling, or pain at the site of injection, occurring in 5-30% of vaccine recipients. More severe reactions are extremely rare.

Impact

Prior to introduction of the conjugate vaccine, Hib was a leading cause of childhood meningitis, pneumonia, and inflammation of the epiglottis in the United States, causing an estimated 20,000 cases a year in the early 1980s, mostly in children under 5 years old. Since routine vaccination began, the incidence of Hib disease has declined by greater than 99%, effectively eliminating Hib as a public health problem. Similar reductions in disease occurred after introduction of the vaccine in Western Europe and developing countries.

Herd immunity

Although Hib vaccine is given to children, Hib infections have also decreased in adults. This decrease occurred because of herd immunity; children infected with Hib carry the bacteria in their nasal passages while clearing the infection. These Hib carrying children would regularly infect adults. Vaccinating children eliminated the source of the bacteria, reducing the rate of Hib in adults.

Recommendations

The CDC and WHO currently recommend that all infants should be vaccinated using a polysaccharide-protein conjugate Hib vaccine, starting after the age of 6 weeks. Specific immunization schedule depends on choice of vaccine and local recommendations.

Vaccination in the developing world

Introduction of Hib vaccine in developing countries lagged behind developed countries for several reasons. The expense of the vaccine was large in comparison to the standard EPI vaccines. Poor disease surveillance systems and inadequate hospital laboratories failed to detect the disease, leading many experts to believe that Hib did not exist in their countries. Finally, health systems in many countries were struggling with the current vaccines they were trying to deliver.

GAVI and the Hib Initiative

To remedy these issues the GAVI Alliance took active interest in the vaccine. GAVI offers substantial subsidization of Hib vaccine for countries who are interested in using the vaccine, as well as financial support for vaccine systems and safe injections. Additionally, GAVI created the Hib Initiative to catalyze uptake of the vaccine. The Hib Initiative uses a combination of collecting and disseminating existing data, research, and advocacy to assist countries in the making a decision abut using the Hib vaccine. Currently, 61 out of 72 low-income countries are planning on introducing the vaccine by the end of 2009. [cite web
title=Hib Initiative
url=http://www.hibaction.org/
accessdate=2008-10-03
quote=61 of 72 GAVI countries have introduced or will introduce Hib vaccine into their routine immunization program ["sic"] by 2009]

References

See also

* Conjugate vaccine
* Epiglottis
* Haemophilus influenzae