UK guidelines for use of erythromycin chemoprophylaxis in persons exposed to pertussis.

Pertussis is well controlled in the UK as a result of an effective vaccination programme. Nevertheless, the disease has not been eliminated, and cases still occur in the most vulnerable group of young infants. Erythromycin chemoprophylaxis has been advocated for use in contacts to prevent secondary cases but the evidence for its use is weak. These guidelines are based on a review of the evidence and aim to help clinicians make more rational decisions on the use of erythromycin chemoprophylaxis for pertussis. Erythromycin has well-established side effects and so its use should be limited to situations where it is likely to be of greatest benefit. If a clinically suspected or confirmed case of pertussis is identified who is also in household contact with someone at greatest risk from pertussis--young infants, especially neonates--then erythromycin chemoprophylaxis should be considered. The aim is to protect those at greatest risk from pertussis by offering chemoprophylaxis to them, to all their household contacts who are unimmunized and to contacts who are 5 years or older if they did not receive a pre-school pertussis booster (not given to those born before 1996 in the United Kingdom). There is no evidence of any benefit from chemoprophylaxis given more than 21 days from the date of onset of the primary case. Unimmunized or partially immunized cases and contacts should complete their course of vaccine.