Frequently Asked Questions (FAQs)General Hib Disease Information:
Epidemiology of Disease:
Vaccine Efficacy: Vaccine Formulations:
Implementation:
Cost Effectiveness: General Hib Disease Information:1. What is Haemophilus influenzae type B (Hib) disease? Haemophilus influenzae type b, abbreviated as Hib, is a bacterium that can cause pneumonia, meningitis (an inflammation of the membranes protecting the brain and spinal cord) and other life-threatening conditions. Hib is responsible for 3 million serious illnesses and an estimated 400 000 deaths per year despite the availability of an effective vaccine. Most Hib disease occurs in developing countries that do not use Hib vaccine. Children under the age of five have the highest risk of Hib disease, with those between four and 18 months of age especially vulnerable. The bacterium was originally thought to cause influenza (which was later discovered to be caused by the influenza virus), which is how it received its name. Hib disease is unrelated to influenza, commonly referred to as the “flu”. Hib bacteria are found in our airways, usually in the nose or upper throat (medically referred to as the nasopharynx). The bacteria are spread through sneezing and coughing. Children often carry Hib bacteria in their nose or throat without showing any signs or symptoms of illness, but they still can pass the bacteria to others. WHO estimates that up to 15% of young children in countries without Hib vaccination programmes may carry Hib bacteria at some time. 3. How long does it take to show signs of Hib disease after being exposed? Most people who are exposed to a person with Hib disease will never become ill. The incubation period from the time of infection to the onset of symptoms is not known; however it may be as short as a couple of days. 4. What are the symptoms of Hib infection? Symptoms range from those of a mild respiratory illness to severe, life-threatening illness. Pneumonia is an infection in the lungs, usually characterized by rapid breathing, cough, and often fever. Severe episodes of pneumonia may cause shortness of breath and visible retraction of the chest below the ribs, also called indrawing. Meningitis is an inflammation of the membranes protecting the brain and spinal cord which may begin with high fever, irritability, neck stiffness and headache. Severe pneumonia and meningitis are life-threatening. Pneumonia and meningitis may be caused by Hib, other bacteria or viruses. Laboratory tests are required to diagnose Hib disease. Hib bacteria can be found in blood or in fluid near the infected area, including fluid from the central nervous system in cases of meningitis. Diagnosing Hib can be quite challenging. The organism is fragile and detection in specimens requires special reagents and proper training. If the child has received antibiotics or if the specimens are not processed quickly and correctly in the laboratory, Hib disease may not be diagnosed.
6. Can Hib disease be treated? Hib disease can be treated with antibiotics. Antibiotic resistance can lead to treatment failure. Early antibiotic treatment can prevent severe disease. Meningitis can cause permanent neurologic damage despite treatment. Many children die needlessly from Hib disease due to lack of access to adequate medical facilities and effective antibiotics. Yes, Hib vaccines are safe. Vaccines are made of parts of the Hib capsule—they cannot cause Hib disease. Children who receive vaccines may have redness, swelling or a feeling of warmth where the injection was given. Some children develop a fever of 101 degrees or higher after vaccination. Severe allergic reactions are rare and may include difficulty breathing, hoarseness, paleness, weakness, and dizziness. 8. Can the Hib vaccine actually cause children to get the disease? No. Vaccines are made of parts of the Hib capsule—they cannot cause Hib disease. Epidemiology of Disease:9. Why focus on Haemophilus influenzae type b? Haemophilus influenzae type b accounted for most (95%) severe disease due to Haemophilus influenzae infections before the introduction of Hib vaccines. In total, there are 6 types (named a, b, c, d, e and f) of Haemophilus influenzae bacteria based on differences in the capsule surrounding the bacteria, while other Haemophilus influenzae bacteria have lost their capsule. All types of Haemophilus influenzae may cause disease, especially in persons with weakened immune systems. Hib vaccines provide specific protection against Hib disease only. Unencapsulated Haemophilus influenzae often cause ear infections and conjunctivitis. 10. Can a child be a carrier of Hib and not be sick? Yes. Before introduction of Hib vaccines, up to 15% of children may carry Hib bacteria in their nose and throat without showing symptoms or becoming sick. Asymptomatic carriers may pass the bacteria to others. Children in child care settings may have high rates of Hib carriage. Higher prevalence of carriage has been shown in certain ethnic groups. Only a minority of Hib carriers will develop Hib infection. 11. What factors increase the risk of Hib disease? Young children (less than 2 years) have the highest rates of Hib disease. Persons with weakened immune systems are at increased risk of Hib disease. Household crowding, exposure to smoke and air pollution and poor nutrition increase a child’s risk of Hib disease, while breast feeding reduces the risk. Certain ethnic groups and native people have high rates of Hib disease. Vaccine Efficacy:12. How well does Hib vaccine work? Available Hib vaccines have been shown in clinical trials to be between 90-100% effective in preventing proven Hib disease. Use of Hib vaccines has dramatically reduced Hib disease in North America and Europe. Effects have been similar in developing countries. 13. Is Hib vaccine effective in HIV positive children? Yes. Hib vaccine prevents Hib disease in HIV-infected children, although not as well as in uninfected children. Children infected with HIV are at high risk of Hib disease and should be vaccinated. Hib vaccination programs have been highly successful in decreasing Hib disease in populations with a high prevalence of HIV infection, as shown in a recent study from Malawi. Vaccine Formulations:14. What formulations are available for Hib vaccine? Hib vaccines are available by themselves or in combination with other antigens, including diphtheria, tetanus and pertussis (DTP) or hepatitis B. Combination vaccines are often preferred by providers and parents because their use reduces the number of injections necessary to be protected against all diseases. The Global Alliance for Vaccines and Immunizations has supported the introduction of a” pentavalent” combination vaccine including DTP, Hepatitis B and Hib in several countries. Presentation of Hib containing vaccines include single and multi-dose vials, in liquid and lyophilized (powder) form. 15. Which Hib vaccine is best suited for use in routine immunization programs? All available Hib vaccines provide protection against Hib disease. Some Hib vaccines are licensed in the U.S. to be given in two doses, others in three doses. A “booster” dose is given in several countries to children after 12 months of age. Combination vaccine products, where affordable, may be advantageous for the immunization program as they require fewer injections. The Global Alliance for Vaccines and Immunization has supported introduction of combination vaccines in several countries. Implementation:16. What are the barriers to universal vaccination against Hib disease? Hib vaccines have been extremely effective when introduced into the routine Expanded Program on Immunizations in developing countries. Barriers to adoption include lack of awareness about Hib disease among decision makers, concerns about costs of adding new vaccines, and competing priorities besides immunization in health budgets. 17. How many countries have introduced Hib vaccines with support from the Global Alliance for Vaccines and Immunization (GAVI)? As of 2007, GAVI is supporting Hib vaccination in 22 of 72 eligible countries. An additional four eligible countries in Latin American introduced Hib vaccines before GAVI was formed. 18. When should a child begin the series of doses? What is the schedule? Children in developing countries generally receive Hib vaccine at 6, 10 and 14 weeks. Schedules may vary by country or depend on the particular manufacturer of the Hib vaccine. 19. Do children need a booster dose? Some countries (mainly industrialized) give children a booster dose at 12-15 months of age. The EPI schedule in developing countries generally does not include a booster dose; however additional surveillance may be needed to determine if the incidence of Hib increases in older age groups and to provide evidence on the need for a booster. Cost Effectiveness:20. Is this vaccine cost-effective? Hib vaccine has been shown to be cost-effective in a number of countries, including developing countries. Vaccines remain one of the best public health buys and benefits are well-beyond the costs that can be measured |
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