Immunization Dialogue

Indian Pediatrics 2000;37: 680-681

Hib Vaccine in the Second Year of Life

Q. What should be the number of doses of Hib vaccine administered to infants between 12 and 15 months of age? The AMA recommends 2 doses (1 primary followed by a booster) for this age group. However, the manufacturers of PRP-T conjugate vaccine (Pasteur Merieux) claim that a single dose of their vaccine provides sufficient immunity in this age group and a booster is unnecessary. Also, is there any difference in the immunogenicity of the various conjugate vaccines available?

K. Banu,
6, Vidyodaya Main Road,
(Behind Vidyodaya School),
Chennai 600 017, India.

The Hib conjugate vaccine use diphtheria or tetanus toxoid or meningococcal outer membrane protein as the protein component. In infants immunized with DPT, it is most likely that one dose of the DT or TT conjugated vaccine will give adequate immune response to the Hib component.

The OMP conjugated Hib vaccine is a better immunogen in its own right. Therefore, in children not previously given DPT, one dose of OMP conjugate will be a better immunogen than DT or TT conjugated Hib vaccine.

I am unable to give evidence-based answer about the antibody levels of one dose versus two doses of each of these vaccines in the 12 to 15 months age group. The American Academy of Pediatrics recommends two doses between 12 and 14 months, but only one dose from 15 months.

In the USA, 3 doses in infancy is followed by one booster in the second year. In the United Kingdom, 3 doses are given during infancy, but no booster in the second year. We need to investigate whether the USA or UK recommendations or another modified version is appropriate in India. I will encourage my younger colleagues in academic institutions to conduct such studies in different parts of India. This will be an excellent topic for MD thesis.

T. Jacob John,
Emeritus Medical Scientist (ICMR),
439, Civil Supplies Godown Lane,
Kamalakshipuram,
Vellore 632 002, India.
E-mail: [email protected]