Liquid PedvaxHIB? - MERCK & CO., Inc. - Marketed Lyophilized Drug Products

Liquid PedvaxHIB? 9018902
[Haemophilus b Conjugate Vaccine
(Meningococcal Protein Conjugate)]
2
? Native Americans14,15,16
? Household contacts of cases17
? Individuals with asplenia, sickle cell disease, or antibody deficiency syndromes18,19
An important virulence factor of the Hib bacterium is its polysaccharide capsule (PRP).
Antibody to PRP (anti-PRP) has been shown to correlate with protection against Hib disease.3,21
While the anti-PRP level associated with protection using conjugated vaccines has not yet been
determined, the level of anti-PRP associated with protection in studies using bacterial
polysaccharide immune globulin or nonconjugated PRP vaccines ranged from >0.15 to
>1.0 mcg/mL.22-28
Nonconjugated PRP vaccines are capable of stimulating B-lymphocytes to produce antibody
without the help of T-lymphocytes (T-independent). The responses to many other antigens are
augmented by helper T-lymphocytes (T-dependent). PedvaxHIB is a PRP-conjugate vaccine in
which the PRP is covalently bound to the OMPC carrier29 producing an antigen which is
postulated to convert the T-independent antigen (PRP alone) into a T-dependent antigen resulting
in both an enhanced antibody response and immunologic memory.
Clinical Evaluation of PedvaxHIB
PedvaxHIB, in a lyophilized formulation (lyophilized PedvaxHIB), was initially evaluated in
3,486 Native American (Navajo) infants, who completed the primary two-dose regimen in a
randomized, double-blind, placebo-controlled study (The Protective Efficacy Study). At the time of
the study, this population had a much higher incidence of Hib disease than the United States
population as a whole and also had a lower antibody response to Haemophilus b Conjugate
Vaccines, including PedvaxHIB.14,15,16,30,33
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