Azithromycin prophylaxis during a hospital outbreak of Mycoplasma pneumoniae pneumonia

Outbreaks of Mycoplasma pneumoniae (MP) in closed communities can have a hi gh attack rate and can last several months. Azithromycin chemoprophylaxis h as not been evaluated as a means of limiting transmission. This randomized, double-blinded placebo-controlled trial of azithromycin was conducted amon g asymptomatic hospital employees during an MP outbreak. Oropharyngeal swab s were obtained for detection of MP by polymerase chain reaction, and quest ionnaires were administered to assess clinical illness. Of the 147 employee s who were enrolled, 73 received azithromycin and 74 received placebo. Carr iage was similar within and between groups at weeks 1 and 6 (9.6% vs. 6.7% and 10.3% vs. 13.2%, respectively). Four episodes of clinically significant respiratory illness occurred in the azithromycin group versus 16 episodes in the placebo group (protective efficacy, 75%; 95% confidence interval, 28 %-91%). Use of azithromycin prophylaxis in asymptomatic persons during an M P outbreak in a closed setting may be of value in reducing clinical illness .