Which of the following statements is true regarding pertussis -

Pertussis (Whooping Cough): Leukocytosis does not correlates with the severity of cough Drug of choice: Erythromycin (40 mg/kg QID X 10 days) Vaccines: DPT: i. Killed acellular bacilli 20,000 million per dose (0.5 ml) ii. Pertussis component leads to neurological complications after 2 years of age (@ 1 per 1,70,000 vaccinees) iii. Vaccine efficacy is 50 – 60 % (2 doses) and 70% (3 doses) Pertussis killed whole cell vaccine DOC for cases and contacts: Erythromycin (for 10 days)