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Canadian Journal of Public Health

, Volume 97, Issue 6, pp 459–464 | Cite as

Pertussis in Rural Populations of Saskatchewan (1995 to 2003)

Incidence, Seasonality, and Differences Among Cases
  • David Vickers
  • Raúl C. Mainar-Jaime
  • Punam Pahwa
Article

Abstract

Background

Few Canadian studies have studied re-emergent pertussis in rural areas. This study described the epidemiology of pertussis in the rural areas of the Saskatoon Regional Health Authority in Saskatchewan, and comparisons were made to the City of Saskatoon.

Methods

Analyses were based on passive surveillance data collected between 1995 and 2003. Estimates of the cumulative incidence (per 10,000 population) measured the occurrence of pertussis. Kaplan-Meier curves were plotted to compare a case’s time until disease from their last vaccination by different vaccine types (whole-cell (WCV), or acellular (ACV)) and vaccine histories (complete or partial). Epidemic curves identified peaks in the incidence and checked for seasonal variation in case reporting.

Results

Over the 9-year period, 1,135 cases were reported. Rural areas had higher incidence rates and lower proportions of cases vaccinated than urban areas. Overall, the highest age-specific incidence was observed in people aged 10–19 years. Cases aged 0–9 years vaccinated with the ACV, from both rural and urban areas, presented a shorter time to disease (14 months (95% CI: 13–16) and 17 months (95% CI: 11–21), respectively) when compared to cases vaccinated with the WCV (47 months (95% CI: 40–51) and 36 months (95% CI: 31–41), respectively), or with a combination of the two vaccines (40 months (95% CI: 27–47) and 44 months (95% CI: 36–51), respectively, p<0.01). Epidemic curves revealed that reported cases are occurring earlier in successive years (1997, 1999, and 2003) in rural areas.

Conclusion

Epidemiologic differences among cases from rural areas exist when compared to urban areas. This study further emphasizes the need to better understand age-, vaccine-, and seasonally-related aspects of pertussis epidemiology in rural areas.

MeSHterms

Epidemiology pertussis rural communities surveillance vaccination 

Résumé

Contexte

Peu d’études canadiennes portent sur la réapparition de la coqueluche en milieu rural. Nous décrivons ici l’épidémiologie de la coqueluche dans les régions rurales couvertes par l’office régional de la santé de Saskatoon, en Saskatchewan, par opposition à la ville de Saskatoon.

Méthode

Nos analyses sont fondées sur les données de surveillance passive recueillies entre 1995 et 2003. Nous avons mesuré la fréquence de la coqueluche d’après les estimations de son incidence cumulative (pour 10 000 habitants). En traçant des courbes de Kaplan-Meier, nous avons comparé le temps écoulé entre la dernière vaccination et l’apparition de la coqueluche, selon les différents types de vaccins reçus (à cellules entières ou acellulaire) et selon les antécédents vaccinaux (complets ou partiels). Des courbes épidémiques ont permis de déceler les pics d’incidence et de vérifier la présence d’écarts saisonniers dans les cas déclarés.

Résultats

Au cours des neuf années de l’étude, il y a eu 1 135 notifications de coqueluche. En milieu rural, les taux de fréquence étaient plus élevés et les proportions de cas vaccinés étaient plus faibles qu’en milieu urbain. Dans l’ensemble, la plus grande fréquence par âge a été observée chez les personnes de 10 à 19 ans. Dans les régions rurales comme dans les agglomérations urbaines, les enfants de 0 à 9 ans ayant reçu le vaccin acellulaire ont contracté la maladie plus rapidement (après 14 mois [IC de 95% = 13-16] et après 17 mois [IC de 95% = 11-21], respectivement) que les sujets ayant reçu le vaccin à cellules entières (après 47 mois [IC de 95% = 40-51] et après 36 mois [IC de 95% = 31-41], respectivement), ou que les sujets ayant reçu une association des deux vaccins (après 40 mois [IC de 95% = 27-47] et après 44 mois [IC de 95% = 36-51), respectivement, p0,01). Les courbes épidémiques montrent que les cas déclarés se sont produits de plus en plus tôt chaque année (1997, 1999 et 2003) dans les régions rurales.

Conclusion

Il existe des écarts épidémiologiques entre les cas des régions rurales et ceux des agglomérations urbaines. L’étude souligne aussi le besoin d’approfondir notre compréhension du rôle de l’âge, des vaccins reçus et des cycles saisonniers dans l’épidémiologie de la coqueluche en milieu rural.

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Copyright information

© The Canadian Public Health Association 2006

Authors and Affiliations

  • David Vickers
    • 1
    • 4
  • Raúl C. Mainar-Jaime
    • 2
  • Punam Pahwa
    • 1
    • 3
  1. 1.Department of Computer ScienceUniversity of SaskatchewanSaskatoonCanada
  2. 2.Department of MicrobiologyWestern College of Veterinary MedicineCanada
  3. 3.Institute of AgriculturalRural, and Environmental HealthCanada
  4. 4.Department of Community Health and EpidemiologyCollege of MedicineCanada

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