Haemophilus influenzae is a gram-negative coccobacillus. It can be divided into encapsulated and non-encapsulated. Non-encapsulated organism is unable to subtype and encapsulated strains can be divided into six serologic types, a-f, of which b type is the most common cause of severe infant disease.
Hib is a serious infectious disease, mainly occurs in children aged less than 5 years. It causes invasive disease such as meningitis, bacteremia, pneumonia, cellulitis, bacterial arthritis, osteomyelitis, and epiglottis, etc. The incidence is considerably different in different regions. The most common presentation of invasive Hib disease is meningitis, which accounted for 50%-65%. The mortality rate is about 2% to 5%. About 15-30% survivors will develop sequelae such as hydrocephalus, encephalitis, ataxia, hearing damage, mental retardation and paralysis. It not only causes severely impact on personal health, but also increases the burden on family as well as the economic costs of the society and country. The conjugated Hib vaccine has been introduced to Taiwan since 1996, and five-in-one vaccine which containing the ingredients of conjugated Hib vaccine is incorporated into Taiwan’s routine vaccination. The incidence of Hib decreases significantly.
- There were 1,058 Hib cases had been reported during 2000 to 2012. The number of cases per year ranged between 38 and 131, with an average of 81 cases. The confirmed cases were 272 cases, the number of cases per year ranged between 3 and 50, and with an average of 21 cases. The male cases were 176 cases (64.7%) and female were 96 cases (35.3%), the male to female ratio was1.83:1.
- National incidence
- The incidence rate ranged from 0.22 to 0.01 cases/100,000 during the year of 2000 to 2012. The annual incidence rate had declined 95% as shown in Figure1.
- Age distribution
- Among 272 confirmed cases, children aged less than 5 years were 159 cases (58.5%), which accounted for the largest number, followed by 5-19 years of 46 cases (16.9%), over the age of 65 years of 30 cases (11%), 40-64 years of 23 cases (8.5%) and 20-39 years of 14 cases (5%). The confirmed cases in all ages had decreased year by year (Figure2).
- Nationwide vaccination of Haemophilus influenzae type b
- The conjugated Haemophilus influenzae type b vaccine had been introduced to Taiwan since 1996, and the self-pay five-in-one vaccine was introduced since 2002, but then the year of birth cohort vaccination was still less than 10%. In 2005, the self-pay five-in-one plus hepatitis B vaccine was introduced, the birth cohort vaccination rate was more than 50% and increased year by year since then. In March 2010, the five-in-one vaccine has been incorporated into national routine vaccination; the vaccination rate was more than 97% (Figure3).
Invasive Haemophilus Influenzae Type b (Hib) Disease Surveillance in Taiwan
Taiwan National Infectious Disease Statistics System - Invasive Haemophilus Influenzae Type b (Hib) Disease
Prevention and Control
- Vaccination is the best way to prevent Hib. Hib vaccine is recommended for all infants who are 2, 4 and 6 month-old, and a boost will be given at 18 month-old.
- The Haemophilus influenzae bacteria spread to other people who have had close or lengthy contact with a patient with Haemophilus influenzae disease. In certain cases, people in close contact with that patient should receive antibiotics to prevent them from getting the disease. This is known as prophylaxis. A doctor or local health department will make recommendations for who should receive prophylaxis.
- Closely contact prevention: If there is any family under 5 years old who never vaccinated with HIB vaccines, all the close contacts should administer Rifampin as prophylaxis.
- In kindergarten or nursing school: If there is a Hib confirmed case occurred in kindergarten, the children and day-care workers in kindergarten should consider to receive antibiotics. If two cases were occurred in the same kindergarten (and there is any child under 2 year-old) within 60 days, all the members in kindergarten should administer the preventive antibiotics under the prescription of doctor.