EFFECTIVENESS AND SAFETY OF AN HAEMOPHILUS-INFLUENZAE TYPE-B CONJUGATE VACCINE (PRP-T) IN YOUNG INFANTS

Objective. To study the safety, immunogenicity, and protective efficac y of the Haemophilus influenzae capsular polysaccharide tetanus conjug ate vaccine (PRP-T). Design. Randomized, double-blind, controlled clin ical trial. Setting. Southern California Kaiser-Permanent Health Plan. Participants. 10 317 infants 6 to 15 weeks of age, with no known immu ne dysfunction, exposure to hepatitis B, or contraindication to diphth eria-tetanus-pertussis (DTP) vaccination were enrolled between August 1989 and September 1990. Intervention. Infants were randomized to rece ive either PRP-T or a recombinant hepatitis B control vaccine (in addi tion to DTP) at approximately 2, 4, and 6 months of age. Outcome measu res. Adverse reactions occurring during the first 72 hours and between doses (including hospitalizations and outpatient visits) were measure d using parental reporting/interviews and review of records. Invasive disease caused by H influenzae was ascertained from the time of enroll ment until December 31, 1990. Results. In October 1990, the study was prematurely terminated because of licensure of other H influenzae vacc ines recommended for routine infant use. The rates of systemic and loc al reactions occurring within 72 hours of each vaccine dose were gener ally similar for infants given PRP-T and hepatitis B, but some reactio n rates (local reactions, fever greater-than-or-equal-to 102-degrees-F , irritability, crying) were significantly higher in the PRP-T group. In the month following receipt of vaccine, PRP-T-vaccinated infants ex perienced five definite seizures compared with three in the hepatitis B control group. Within 48 hours of vaccination, three seizures (two d efinite and one possible), which were thought to be related to vaccina tion, occurred in the PRP-T group, compared with none in the control g roup (P < .13). Overall morbidity, mortality, and hospitalization rate s were similar in the two vaccine groups. Three cases of invasive dise ase caused by H influenzae occurred in the control group; none occurre d in the PRP-T group. Conclusions. The PRP-T vaccine is safe and appea rs to be effective in preventing invasive disease caused by H influenz ae type b.