Safety & Immunogenicity of Hib vaccine in combination with DPT:- When Hib vaccine (PRP-T) was given in combination with DPT at 6, 10 and 14 weeks of age it was found to be safe and immunogenic and was well tolerated. So it may be suitable for inclusion in WHO EPI schedule.

DPT with Hib vaccine Vs DPT-Hib combination: As the combination vaccine is costly so one study was conducted to evaluate the effects of DPT vaccine (local) mixed with Hib vaccine Vs combination vaccine. Combining Hib vaccine and a local DPT did not affect the anti Hib response so it seemed a reasonable option for our country. However use of combination vaccine would be preferable because of lower reactogenicity and superior immunogenicity with respect to diphtheria and tetanus.

Hib Vaccine and Prematurity: A recently conducted study concluded that though premature infants develop lower antibodies concentration then term infants following Hib conjugate vaccination, it still provides a high level of protection to premature babies. Study pointed that they may also have increased risk of clinical vaccine failure.

Hib Vaccine and Immunodeficiency states: Studies have shown that children at increased risk for Hib disease because of severe combined immunodeficiency syndrome (SCID) or IgG2 deficiency, symptomatic HIV infection, patients on chemotherapy may not develop protective antibodies from the vaccine and may or may not benefit from additional dose.

Hib vaccine is one of only two vaccines that are more effective at providing immunity than natural infection. The other is tetanus vaccine.

Healthy recipients of Hib conjugate vaccine may be susceptible to Hib disease for 1-2 weeks until antibodies are developed.

• The commercially available Hib conjugate vaccines are all of known good quality and offer protection of children below 5 years of age, especially infants.
  
  
• WHO recommends the Hib vaccine introduction worldwide.
  
  
• Various studies have shown that Hib vaccine do not interfere substantially with the immunogenicity of simultaneously given vaccines e.g. DPT, Hepatitis B. So Hib vaccine can be easily adapted to a routine national immunization schedule.
  
  

• Hib vaccine should be offered to all children and can be given at 6, 10 and 14 weeks along with DPT. A booster is given at 15-18 months.
  
  
• If vaccination is started (commenced) after 6 months of age, only 2 doses at 8 weeks interval need to be given as primary schedule with a booster at 15-18 months.
  
  
• After 12-15 months one dose should be given with booster at 18 months.
  
  
• After 15 months of age only one dose of the vaccine is adequate and booster dose is not required.
  
  
• Hib vaccine is also recommended for all children, prior to splenectomy and in patients with sickle cell disease irrespective of age.
  
  

1. Hussey G, Malan H, Hughes J et al. Safety and immunogenicity of TETRActHIB (a vaccine combining DTP vaccine and Haemophilus influenzae type B conjugate vaccine) administered to infants at 6, 10 and 14 weeks of age. S Afr Med J 2002;92(1):53-7.
2. Foxwell AR, Cripps AW, Dear KB. Haemophilus influenzae oral whole cell vaccination for preventing acute exacerbations of chronic bronchitis. Cochrane Database Syst Rev 2003;(3):CD001958.
3. Cherian T, Thomas N, Raghupathy P et al. Safety and immunogenicity of Haemophilus influenzae type B vaccine given in combination with DTwP at 6, 10 and 14 weeks of age. Indian Pediatr 2002;39(5):427-36.
4. Heath PT, Booy R, McVernon J et al. Hib vaccination in infants born prematurely. Arch Dis Child 2003;88(3):206-10.
5. Madhi SA, Petersen K, Khoosal M et al. Reduced effectiveness of Haemophilus influenzae type b conjugate vaccine in children with a high prevalence of human immunodeficiency virus type 1 infection. Pediatr Infect Dis J 2002;21(4):315-21.
6. Core information for the development of Immunization Policy. WHO- Vaccines and Biologicals. 2002 Update
7. Update on Immunization Policies, Guidelines and Recommendation. Indian Pediatrics2004; 41: 239-244.