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 pertus sis, we studied am children <2 years of age who were admitted to the 11 Imm unization Monitoring Program-Active (IMPACT) centers, which constitute 85% of Canada's tertiary care pediatric beds. In the 7 years preceding implemen tation of acellular pertussis vaccine, a total of 1,082 pertussis cases wer e reported, of which 49.1% were culture-confirmed. The median age of the pa tients was 12.4 weeks; 78.9% of cases were in children <6 months of age. Co mplications of pertussis were common: pneumonia was reported in 9.4% of cas es,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 h ospitalization was longer (9.3 days vs. 4.9 days; P = .001) and intensive c are was required more frequently (19.2% vs. 4.9%; P = .001) in infants unde r <6 months of age than in those greater than or equal to 6 months. Pertuss is continues to cause significant morbidity and occasional mortality in Can ada, particularly in young infants.