Table 4.

Efficacy of Erythromycin Prophylaxis in Household Members Without Symptoms Compatible With Pertussis at the Time of Initiation of Treatment

OutcomeCase Definition
Culture-positive (C+)C+ or Paroxysmal
Cough ≥2 Weeks
C+ or Cough ≥2 Weeks
and ≥1 Symptom*
ErythromycinPlaceboErythromycinPlaceboErythromycinPlacebo
Total household contacts144166144166144166
 Secondary cases51626423653
  Before prophylaxis2820342845
  After prophylaxis386888
Postprophylaxis SAR,§ 3/142 (2.1%)8/158 (5.1%)6/124 (4.8%)8/132 (6.1%)8/116 (6.9%)8/121 (6.6%)
  • * Pertussis symptoms include paroxysms or vomiting with cough, whoop, apnea, or cyanosis.

  • Secondary attack rate = (cases/contacts) × 100.

  • § P ≥ .20 in all three group comparisons.