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Can Hib cause injury and death?
Prior to the introduction of vaccines targeting H. influenzae type b (Hib), between 0.5 and 3 percent of infants and children were found to have Hib present in the upper respiratory tract and Hib bacteria were rarely found in adults. Most children colonized Hib and developed immunity to it by the age of 6 as a result of being asymptomatic carriers. Currently, Hib is believed to colonize in the back of the throat of between 3 and 5 percent of children.
The presence of Hib in infants and young children infrequently results in serious invasive disease that can include:
- Meningitis – an infection of membranes that cover the spinal cord and brain
- Cellulitis – a serious bacterial infection of the skin
- Epiglottitis – an infection that causes swelling of the epiglottis, with the potential to cause airway obstruction
- Septic arthritis – an infection of the joint
- Pneumonia – a lung infection
- Osteomyelitis – an infection of the bone
- Pericarditis – an infection of the sac that covers the heart
The precise mechanism in which Hib invades the bloodstream to become invasive is not known, however, it is thought that a preceding infection involving the respiratory system may play a key role. Prior to the introduction of Hib vaccines, children under the age of one accounted for approximately 60 percent of invasive Hib disease infections, with the majority of cases impacting infants between 6 and 11 months of age. Additionally, Hib meningitis was reported to be the most common presentation of invasive Hib disease and responsible for 50-65 percent of cases. An estimated 8,000 to 11,000 Hib meningitis cases occurred each year and 3 to 7 percent resulted in death. 15 to 30 percent of survivors had long-term neurological or hearing impairments as a result of the disease.
Hib vaccine does not offer protection against any other type of H. influenzae strains, and additional types of encapsulated strains of H. influenzae can cause invasive disease similar to Hib, including meningitis. While nontypeable (unencapsulated) strains are more likely to cause illnesses such as bronchitis and otitis media in children, they also have the potential to cause serious invasive disease. Currently among all age groups, non-typeable H. influenzae is responsible for the majority of all cases of invasive H. influenzae disease. Nontypeable strains of H. influenzae are commonly found in the nasal passages of most infants, children, and adults.
IMPORTANT NOTE: NVIC encourages you to become fully informed about Haemophilus Influenzae Type B (Hib) and the Hib vaccine by reading all sections in the Table of Contents, which contain many links and resources such as the manufacturer product information inserts, and to speak with one or more trusted health care professionals before making a vaccination decision for yourself or your child. This information is for educational purposes only and is not intended as medical advice.