Lack of efficacy of Haemophilus b polysaccharide vaccine in Minnesota

We evaluated the efficacy ofHaemophilusb polysaccharide vaccine in children in Minnesota using a case-control study. The vaccine became available in Minnesota in August 1985. During the subsequent 28 months, 88 cases of invasiveH influenzaetype b disease were identified in children 24 to 71 months of age, the group targeted for vaccination. Of the 88 cases, 36 (41%) occurred in vaccinated children. Fifty-eight (33%) of 176 controls were vaccinated during a similar period. The vaccine's protective efficacy for children with any history of vaccination was -58% (95% confidence interval = -204% to 18%). The vaccine's protective efficacy for children who were most likely to be protected by vaccination was -55% (95% confidence interval = -238% to 29%). Our results indicate that vaccination withHaemophilusb polysaccharide vaccine had no effect in preventingH influenzaetype b disease in Minnesota children. (JAMA1988;260:1423-1428)