A Cochrane review included 24 studies between the years 1966 to 2000. In 19 studies 2 531 persons were randomized. Five studies used cluster randomization (households and military companies) including 4 354 persons. Fifteen studies compared an antibiotic drug given orally or intra-muscularly to placebo or no intervention. Eleven studies compared different antibiotic drugs. Ciprofloxacin (RR 0.04, 95% CI 0.01 to 0.12), rifampin (rifampicin; RR 0.17, 95% CI 0.13 to 0.24), minocycline (RR 0.28, 95% CI 0.21 to 0.37) and penicillin (RR 0.47, 95% CI 0.24 to 0.94) proved effective at eradicating N. meningitidis one week after treatment, compared with placebo. However, after one to two weeks only rifampin (RR 0.20, 95% CI 0.14 to 0.29), ciprofloxacin (RR 0.03, 95% CI 0.00 to 0.42) and penicillin (RR 0.63; 95% CI 0.51 to 0.79) still proved effective. Rifampin was effective compared to placebo up to four weeks after treatment but resistant isolates were seen following prophylactic treatment. Ceftriaxone was more effective than rifampin, after one to two weeks of follow up (RR 5.93, 95% CI 1.22 to 28.68). No trials evaluated ceftriaxone against placebo. Rifampin continued to be effective compared to placebo until up to four weeks of post treatment follow up but resistant isolates were seen following prophylactic treatment.
There were no cases of meningococcal disease during follow up in any of the trials, thus effectiveness regarding prevention of future disease cannot be directly assessed.