Effect of Early Administration of Clarithromycin or Azithromycin on Symptoms of Pertussis in Infants

Background: A resurgence of pertussis has been observed in several geographic areas in the post-COVID-19 era. Macrolides are the first-choice antibiotics for the treatment of pertussis. Limited data exist on the impact of the early administration of clarithromycin or azithromycin on infants' pertussis symptoms. Methods: This retrospective cohort study analyzed infants enrolled in an enhanced surveillance program for pertussis at a single Italian clinical reference center between 2015 and 2020. All cases were laboratory-confirmed. This study compared outcomes based on the timing of macrolide antibiotic treatment: early administration (within 7 days of cough onset) versus late administration (8 days or later). Key outcomes included cough duration, symptom frequency, and complication rates. Results: We studied 148 infants with confirmed pertussis. The median duration of coughing was 14 days in infants with early administration and 24 days in those with late administration. The occurrence of symptoms differed for apnea (62.6% for early administration; 84.6% for late administration). In a multivariable Cox model, the duration of the cough was lower in infants receiving antibiotics within 7 days from the beginning of the cough compared with those starting later (HR = 0.36, 95% CI: 0.25-0.53, p < 0.001). Clarithromycin was associated with a shorter duration of coughing (HR = 0.42, 95% CI: 0.19-0.92, p = 0.030) independently from other factors. Regarding the occurrence of symptoms, c