EFFICACY OF HAEMOPHILUS-INFLUENZAE TYPE-B CONJUGATE VACCINE PRP-T

Efficacy of the Haemophilus influenzae type b (Hib) conjugate vaccine PRP-T (Pasteur-Merieux) was evaluated in a controlled community interv ention study in the Oxford region, UK. PRP-T was offered to infants fr om May 1, 1991 in three of the region's eight districts and from July 1, 1998, in a fourth district. It was given by separate injection in a ddition to the standard diphtheria, tetanus, and pertussis vaccine acc ording to an accelerated 2, 3, and 4 month schedule without a booster dose in the second year of life. By October 1, 1992, more than 90% of infants in vaccine districts had received at least one dose of PRP-T. None of the infants given three doses had developed Hib infection, whe reas 11 infections occurred in the control population (vaccine efficac y 100%, 95% Cl 80-100%). Intention-to-treat analysis also showed a hig h estimate of efficacy for the vaccine (90%, 50-99%). Follow-up of stu dy children until November 1, 1993, has shown only 1 vaccine failure i n an infant, and no invasive infections in those older than 1 year (av erage age 22 months). PRP-T vaccine had high protective efficacy with an accelerated immunisation schedule. Furthermore, the vaccine appears to remain protective through the second year of life without a booste r dose. These findings provide encouragement for use of PRP-T in the E xpanded Programme of Immunisation.