CLINICAL AND SEROLOGIC RESPONSES OF SAUDI CHILDREN TO HAEMOPHILUS-INFLUENZAE TYPE-B CAPSULAR POLYSACCHARIDE DIPHTHERIA TOXOID CONJUGATE VACCINE

Sixty-eight Saudi children, 17 to 19 months of age. were enrolled in a study to evaluate the safety and immunogenicity of Hemophilus influen zae type B capsular polysaccharide diphtheria toxoid (PRP-D) conjugate vaccine. Adverse reactions to the vaccine were determined through a q uestionnaire administered to the parents. Local and systemic reactions to the vaccine were mild and resolved within 24 to 48 hours. PRP anti body levels were measured prior to and one to two months following imm unization. PRP antibody levels in the pre-immunization sera of 77% of subjects were below the level associated with immediate protection (gr eater-than-or-equal-to 0.15 mug/ml), and 88% were below the level asso ciated with long-term protection (greater-than-or-equal-to 1 mug/ml) f rom Hemophilus influenzae type B (HIB) disease. After one dose of PRP- D vaccine, 100% of recipients achieved antibody levels of greater-than -or-equal-to 0.15 mug/ml, and 85% achieved levels of greater-than-or-e qual-to 1 mug/ml. The geometric mean level of antibody after immunizat ion (5.66 mug/ml) was significantly higher than that before immunizati on (0.098 mug/ml). All subjects had a twofold or greater increase in a ntibody level in response to the vaccine. We conclude that PRP-D is a safe and highly immunogenic vaccine in this age group of Saudi childre n.