What is it?

Haemophilus influenzae is a type of bacteria that can live in a person’s nose and throat. It is considered part of the normal flora of the nasopharynx (upper respiratory tract) and generally does not cause symptoms of disease. However, when the bacteria invade other areas of the body, severe infections and complications can occur. Encapsulated strains of haemophilus influenzae (bacteria with distinct polysaccharide capsules) are more likely to cause invasive infections than non-encapsulated subtypes (those without polysaccharide capsules). Of the 6 encapsulated subtypes (named A-F), type B (Hib) is the only vaccinepreventable strain.  

What to look for

The symptoms of an invasive Hib infection will depend on the location of the infection (e.g., brain, lungs). 

Meningitis (brain inflammation) is the most common presentation of an invasive Hib infection and is often accompanied by bacteraemia (blood infection). Invasive infections can also manifest as otitis media (ear infections), epiglottitis (swelling of the throat), pneumonia (lung infections), arthritis (joint infection), cellulitis (skin infection), osteomyelitis (inflammation to the bone) and pericarditis (inflammation to the sac surrounding the heart).  

Even with treatment, 3% of Hib meningitis cases occurring in developed countries will be fatal, and 10-30% of cases will have permanent neurological complications.  

How can it be transmitted?

Hib can be passed from person to person through inhaling the respiratory droplets of an infected person (produced from coughing or sneezing). In some instances, it can also be transmitted by direct contact with infectious secretions (e.g., touching nasal mucous on a tissue or surface). 

Carriers may be symptomatic or asymptomatic. A person can transmit the bacteria for as long it is present in the nasopharynx. 

Epidemiology

Before vaccination was included on the National Immunisation Program (NIP) in 1992, Hib was the biggest cause of invasive bacterial infection in children in Australia. Since then, the number of Hib infections notified has reduced by 95%. 

Aboriginal and Torres Strait Islander children have a much greater burden of disease than the non-Indigenous population.  

Asplenia and hyposplenia are conditions associated with a lifelong risk of bacterial infections. Individuals with these conditions are therefore at a greater risk of invasive disease if they have not been appropriately immunised. 

Prevention

Protection is offered through the intramuscular administration of inactivated, conjugate vaccines (combination and single antigen vaccines). They are provided on the NIP at: 

  • 6 weeks, 4 months, and 6 months- Infanrix® hexa/Vaxelis® 
  • 18 months- ActHIB®  

NB: Children <5 years of age with asplenia and hyposplenia should be up to date with the routine schedule and if not, they should be offered catch-up. Those aged 5 years and over who did not complete their primary course of vaccination should receive a single dose of Hib-containing vaccine. 

Vaccine side effects

Injection site reactions and fever have been reported following administration of Hib-containing vaccines. Symptoms usually appear within the first 4 hours and resolve within 24 without the need for intervention or additional monitoring. 

Authors: Georgina Lewis (Clinical Manager SAEFVIC, Murdoch Children’s Research Institute) and Rachael McGuire (MVEC Education Nurse Coordinator)

Reviewed by: Rachael McGuire (MVEC Education Nurse Coordinator)

Date: July 4, 2023

Materials in this section are updated as new information and vaccines become available. The Melbourne Vaccine Education Centre (MVEC) staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family’s personal health. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult a healthcare professional.