Functional antibody activity elicited by fractional doses of @entity327 type b conjugate vaccine ( XXXX - @entity116 toxoid conjugate).

@entity13672 @entity1 @entity14672 @entity327 @entity116 @entity11872
We evaluated the functional activities of antibodies, serum bactericidal activity (SBA), and immunoglobulin G (IgG) antibody avidity indices, using @entity13672 ( @entity13672 ) elution, elicited after vaccination with fractional doses of the @entity327 type b conjugate ( @entity11872 [ @entity14672 ] conjugated to @entity116 toxoid [PRP-T]) vaccine. A cohort of 600 @entity1 from the Dominican Republic were randomized to receive one of three regimens of the PRP-T vaccine at ages 2, 4, and 6 months: full doses (10 microg of PRP antigen), one-half doses (5.0 microg), and one-third doses (3.3 microg) (J. Fernandez et al., Am. J. Trop. Med. Hyg. 62:485-490, 2000). Sixty serum samples, collected at age 7 months, with > or =2.0 microg of anti-PRP IgG per ml were randomly selected for avidity determinations. Geometric mean IgG concentrations were 13, 14, and 17 microg/ml for @entity1 who received the full-dose (n = 19), one-half-dose (n = 19), and one-third-dose (n = 22) regimens, respectively. SBA geometric mean titers (1/dilution) were 85.0, 82.0, and 76.1 in sera from @entity1 receiving the full-, one-half-, and one-third-dose regimens, respectively. Avidity indices (mean +/- standard error weighted average of @entity13672 molar concentration x serum dilution factor) were 71.9 +/- 9.4, 123.6 +/- 26.8, and 150.9 +/- 24.9 for the full-, one-half-, and one-third-dose regimens, respectively. Upon comparison, the only significant difference (P = 0.024) found was a greater avidity index for sera from @entity1 receiving the one-third-dose regimen than for sera from @entity1 receiving the the full-dose regimen. We conclude that fractional doses elicit similar functional antibody activities in @entity1 with > or = 2 microg of anti-PRP IgG per ml, corresponding to 89, 90, and 97% of @entity1 receiving three doses of either the full concentration or one-half or one-third of the labeled concentration, respectively. This approach offers an alternative strategy for the prevention of @entity327 type b disease in countries with limited resources.
