Epidemiological features of pertussis in hospitalized patients in Canada, 1991-1997:: Report of the Immunization Monitoring Program-Active IMPACT)

To assess the morbidity associated with the continued high levels of pertussis, we studied am children <2 years of age who were admitted to the 11 Immunization Monitoring Program-Active (IMPACT) centers, which constitute 85% of Canada's tertiary care pediatric beds. In the 7 years preceding implementation of acellular pertussis vaccine, a total of 1,082 pertussis cases were reported, of which 49.1% were culture-confirmed. The median age of the patients was 12.4 weeks; 78.9% of cases were in children <6 months of age. Complications of pertussis were common: pneumonia was reported in 9.4% of cases,new seizures in 2.3%, and encephalopathy in 0.5%. There were 10 deaths (0.9%), all in children less than or equal to 6 months of age. Duration of hospitalization was longer (9.3 days vs. 4.9 days; P = .001) and intensive care was required more frequently (19.2% vs. 4.9%; P = .001) in infants under <6 months of age than in those greater than or equal to 6 months. Pertussis continues to cause significant morbidity and occasional mortality in Canada, particularly in young infants.