Haemophilus influenzae type b (Hib) is an important cause of childhood meningitis and pneumonia. It is estimated to cause at least 3 million cases of invasive disease and around 700,000 deaths worldwide annually.
Expression of the polysaccharide capsule increases bacterial virulence and is associated with severe disease. Vaccination confers protection by induction of anticapsular antibodies and immunological memory. Conjugate Hib vaccines were introduced during the 1990s and are considered safe and highly efficacious.
Efficacy and coverage
The introduction of the Hib conjugate vaccine in the UK has resulted in more than 90% reduction in the incidence of invasive Hib disease.
The clinical efficacy of the conjugate Hib vaccines is estimated as 83-100%.The vaccination also reduces nasopharyngeal carriage in asymptomatic carriers and therefore confers herd immunity to unvaccinated children.
One analysis has shown that approximately three quarters of meningitis deaths are preventable with the existing Hib vaccine and pneumococcal conjugate vaccine (PCV).
Although Hib and pneumococcal vaccines have been available for more than a decade in developed countries, they have only recently been made available to children in low-income countries through financial support from the GAVI Alliance. Nearly all low-income GAVI-eligible countries have Hib conjugate vaccine included in their national immunisation programmes.
Conjugate Hib vaccination was introduced into the UK routine childhood immunisation schedule in 1992. In 1996, the single Hib vaccine was replaced by a diphtheria, tetanus, pertussis and Haemophilus influenzae type b (DTP/Hib) combination. The original DTP/Hib combination was replaced by the current diphtheria, tetanus, acellular pertussis/inactivated polio/Haemophilus influenzae type b (DTaP/IPV/Hib) vaccine in 2004.
The choice of Hib-containing vaccine to be used at different ages will depend on what other immunisations the child has already received and on the availability of suitable preparations.
The introduction of immunisation in the UK caused an immediate decline in the incidence of Hib. The control of Hib disease in the UK is currently the best that has been achieved since the introduction of the routine Hib vaccination.There has since been a gradual reduction in cases of Hib. There has been a decline in the number of cases among those aged 15 years and over from 17 in 2013 to 9 in 2014 (47% decrease).
There have been no deaths due to invasive Hib disease since 2011; the most recent death in a child aged under 16 years, attributed to invasive Hib disease, was in 2011.
Hib vaccines are composed of capsular polysaccharide from cultured Haemophilus influenzae type b bacteria, conjugated to protein to strengthen immunogenicity.
The Hib vaccine is available as:
- DTaP/IPV/Hib vaccine.
- Hib/meningitis C (Hib/MenC) combined vaccine.
Although the current DTaP/IPV/Hib vaccine contains an acellular pertussis component, the preparation does induce an effective immunological response to Hib antigens.
Hib vaccines are injected intramuscularly. Upper arm or anterolateral thigh sites are recommended to minimise the risk of local reactions. Other vaccinations such as measles, mumps, rubella (MMR), MenC or hepatitis B can be given at the same time but should be injected at an alternative site and preferably in a different limb.
The Infanrix-IPV + Hib® is a combination vaccine that protects infants against diptheria, tetanus, whooping cough, polio and Haemophilus influenzae type b. This vaccine requires reconstitution before being administered, whereas the alternative, Pediacel®, is in a pre-filled syringe.
There is no evidence that the immune responses elicited by the combined vaccine are any different from or equivalent to the separate vaccines.
All infants should receive the primary Hib immunisation course. The DTaP/IPV/Hib vaccine is given at 2, 3 and 4 months of age.
Children also receive a booster of Hib (as Hib/MenC) vaccine at 12 months (given at the same time as MMR and PCV). If primary immunisation has been delayed, children up to 10 years of age can be given three doses of combination vaccine at monthly intervals. Although only one dose of Hib vaccine is necessary to achieve immunity in children aged over 1 year, the extra doses are required to provide immunity to diphtheria, tetanus, polio (and pertussis if given).
Adults and children aged over 1 year who have completed a primary course of diphtheria, tetanus, pertussis and polio but have not received Hib-containing vaccines, should be given a single dose of Hib/MenC vaccine.
Children from developing countries may not have received the vaccination. If the history is unclear, children are considered unimmunised and should complete the full UK schedule.
Splenic dysfunction or complement deficiency
These Individuals are at increased risk of invasive Hib infection:
- Children under 2 years of age should complete the primary immunisation course including Hib/MenC at 12 months, and then a MenACWY conjugate vaccine at least a month after the MenC.
They also need a second Hib/Men C after their second birthday, with a pneumococcal booster - pneumococcal polysaccharide vaccine (PPV). (NB: if their previous PCV booster dose was PCV7 rather than PCV13 (before April 2010), they need two pneumococcal vaccines - give PCV13 first, with a PPV two months later.)
- Children aged 2-5, having completed the normal primary course and one booster, aged around 1 year, need a Hib/MenC booster with a PCV13 booster (as they will have had PCV7), followed by a MenACWY conjugate vaccination a month later and a PPV booster a further month afterwards.
- Children aged over 5 and adults need a Hib/MenC booster with a PPV booster, followed by a MenACWY conjugate vaccine a month later.
Patients undergoing splenectomy should ideally be offered the vaccines two weeks before surgery, or as soon as possible postoperatively.
Unimmunised patients with diagnosed Hib infections should be immunised, as recurrence of disease can occur. Patients who have been immunised but later acquire Hib infection may benefit from a booster dose of vaccine, depending on convalescent antibody levels.
Children who are household contacts of an index case should be fully immunised as per previous recommendations.
The vaccination should not be administered to individuals with:
- Confirmed anaphylactic reaction to a previous dose of the Hib-containing vaccine.
- Confirmed anaphylactic reaction to any components of the vaccine.
The following situations do not prohibit vaccination:
- History of a stable neurological condition, seizures or febrile convulsions (without neurological deterioration).
- As there is no evidence of increased risks of adverse reactions from vaccinations in preterm babies, premature infants should receive vaccinations at appropriate chronological age, according to the schedule.
- Fever, persistent screaming, severe local reactions or hypotonic-hyporesponsive episodes following previous Hib-containing vaccinations.
- Immunosuppression including HIV infection (but individuals may not achieve an adequate immunological response and may benefit from re-immunisation).
- Pregnancy or breast-feeding.
Further reading and references
Thumburu KK, Singh M, Das RR, et al; Two or three primary dose regime for Haemophilus influenzae type b conjugate vaccine: meta-analysis of randomized controlled trials. Ther Adv Vaccines. 2015 Mar3(2):31-40. doi: 10.1177/2051013615575871.
Davis S, Feikin D, Johnson HL; The effect of Haemophilus influenzae type B and pneumococcal conjugate vaccines on childhood meningitis mortality: a systematic review. BMC Public Health. 201313 Suppl 3:S21. doi: 10.1186/1471-2458-13-S3-S21. Epub 2013 Sep 17.
Haemophilus influenzae type b vaccine support; Gavi - The Vaccine Alliance
Immunisation against infectious disease - the Green Book (latest edition); Public Health England
Ladhani SN; Two decades of experience with the Haemophilus influenzae serotype b conjugate vaccine in the United Kingdom. Clin Ther. 2012 Feb34(2):385-99. doi: 10.1016/j.clinthera.2011.11.027. Epub 2012 Jan 12.
Haemophilus influenzae: epidemiological data; Public Health England, February 2015
Bar-On ES, Goldberg E, Hellmann S, et al; Combined DTP-HBV-HIB vaccine versus separately administered DTP-HBV and HIB vaccines for primary prevention of diphtheria, tetanus, pertussis, hepatitis B and Haemophilus influenzae B (HIB). Cochrane Database Syst Rev. 2012 Apr 184:CD005530. doi: 10.1002/14651858.CD005530.pub3.
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