Results of an efficacy trial with an outer membrane vesicle vaccine against systemic serogroup B meningococcal disease in Norway.

A placebo controlled, double blind efficacy trial with a new outer membrane vesicle vaccine against systemic meningococcal disease of serogroup B, has been conducted in Norwegian secondary schools. The study was randomized at school level (1335 schools) and 171,800 students volunteered. The study started in October 1988 and the code was opened in June 1991. Out of the thirty-six proven cases of acute, severe, systemic disease caused by serogroup B meningococci among the participants, twelve occurred in eleven schools given vaccine, twenty-four in twenty-four schools given placebo. twenty-four cases were recorded among secondary school students who did not participate in the study. The protection rate was calculated to 57.4% with a p-value of 1.2% and lower limit of confidence (95%) to 27.7%. The results have initiated research towards an improved outer membrane vesicle vaccine against this disease.