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Between July 1997 and April 1998, universal childhood immunization programs in Canada changed from using a whole-cell pertussis to a 5-component acellular pertussis-containing vaccine. To assess effects on pertussis epidemiology of this nationwide change, we analyzed hospitalizations during 1991-2004 using the Canadian Immunization Monitoring Program, Active (IMPACT) pertussis database.IMPACT is an active surveillance network based in 12 pediatric tertiary-care hospitals across Canada. Characteristics of hospitalized cases of pertussis were compared by type of vaccine received or by birth date (if immunization records were unavailable or the child was unvaccinated). Age-stratified incidence rates were calculated by year and vaccine type.Two thousand ninety-six cases of pertussis were admitted to IMPACT centers, 1174 during the whole-cell vaccine program (WCV-P) and 842 during the acellular vaccine program (ACV-P). Pertussis incidence among children5 years old decreased significantly during the ACV-P, causing an increase in the residual proportion of cases either too young to be immunized (2 months old: ACV-P 39% versus WCV-P 26.1%; P0.0001) or too young for a second dose (2-3 months old: 42.9% versus 34.2%, respectively; P0.0001). A significantly smaller proportion of cases (ACV-P 15.1% versus WCV-P 27.3%) occurred in infants who were old enough (4-11 months of age) to have received 2 or 3 doses of vaccine.With ACV-P, pertussis hospitalizations in children 4-59 months old decreased in frequency, consistent with improved vaccine effectiveness, but remained prominent among very young infants. Improved control strategies are needed to reduce infections among infants too young for pertussis vaccination.

A resurgence of pertussis has been observed in Canada, the United States and Australia since the 1980s, but inconsistent data are currently available for Europe. The objective of this paper is to describe the epidemiology of pertussis in Western European countries to discuss future vaccination strategies.The European Community funded a network for the epidemiologic surveillance of measles and pertussis in 1998. Sixteen European countries provided national surveillance data for pertussis for the period 1998-2002 in a standard format. Data were pooled and analyzed to describe incidence rates by age group, seasonality, proportion of hospitalized patients and deaths among notified cases.Children younger than 1 year had the highest incidence during the entire period. Rates in the older than 14 years age group increased by 115% during the study period. Northern countries showed the highest incidence figures in all age groups. Among children younger than 1 year, 70% were admitted into hospital. Children younger than 6 months of age and those not vaccinated were most likely to be hospitalized. Thirty-two deaths were reported, 87% of which were in children younger than 6 months of age.Pertussis is far from being controlled in Europe. Whereas the incidence in children younger than 1 year was high but remained stable, rates in adults doubled in 5 years.

In Australia in 1999 acellular pertussis vaccine (DTPa) replaced locally manufactured whole cell vaccine given at 2, 4 and 6 months of age with coverage of about 95% by 12 months of age. Few data are available on pertussis hospitalizations or sources of infection in countries exclusively using DTPa.In 2001 national active monthly surveillance of infant hospitalizations for pertussis was conducted through the Australian Pediatric Surveillance Unit, which surveys all child health specialists monthly. A standard questionnaire was completed for notified cases.There were 140 infants reported (median age at diagnosis, 8 weeks). The rate of hospitalization in indigenous infants was significantly higher than in nonindigenous infants (P0.01). Of 97 (69%) infants who had not been vaccinated for pertussis, 63 (65%) were8 weeks old (before the first scheduled dose of DTPa vaccine). Of 76 infants ageor =8 weeks, only 28 (37%) were appropriately immunized for age. Of 68 coughing contacts whose ages were known, 46 (68%) were adults, usually one of the infant's parents. Of 32 child contacts 16 (50%) were siblings. Four infants6 weeks old died.Despite universal vaccination with DTPa in Australia, pertussis remains an important cause of hospitalization, morbidity and death in infants, most of whom were too young to be vaccinated or had missed vaccinations. The most common source of infection was a parent. Strategies to improve pertussis control in countries with high DTPa coverage could include adult-formulated booster pertussis vaccines for adolescents and recent parents and/or accelerated pertussis vaccine schedules for infants.

Pertussis admissions ranged from 0 to 7.4 per 10,000 hospitalizations from 1996 to 2003, and from 16.3 to 27.4 per 10,000 hospitalizations from 2004 to 2006. A total of 78% of patients were