Absolute contraindications to pertussis immunization should be limited to anaphylaxis or unexplained encephalopathy following a previous dose. Other contraindications including marked febrile reactions (> 40.5 degrees C), hypotonic-hyporesponsive episodes, prolonged screaming (> 3 h) and severe local reactions (more than half the limb involved) are relative, as no long-term adverse consequences have been noted, and must be weighed up in the context of the risk of pertussis to the individual child. Each of these contraindications will affect less than 1% of children. Paediatricians should strongly discourage the inappropriate deferral of pertussis immunization due to mild illness and the omission of pertussis vaccine because of inappropriate contraindications, such as many of those mentioned in the product information. This is especially important in children who have underlying conditions which may place them at greater risk of acquisition of and complications from natural pertussis infection.