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.
Footnotes
Acknowledgements: Funding for this paper was made possible by the Founding Chairs Graduate Fellowship courtesy of the Institute of Agricultural, Rural, and Environmental Health, University of Saskatchewan.
Disclaimer: This paper was based on non-identifiable data. The interpretations and conclusions contained in this paper do not necessarily represent those of the Saskatoon Regional Health Authority or of Saskatchewan Health
References
- 1.Broutin H, Guegan JF, Elguero E, Simondon F, Cazelles B. Large-scale comparative analysis of pertussis population dynamics: Periodicity, synchrony, and impact of vaccination. Am J Epidemiol. 2005;161:1159–67. doi: 10.1093/aje/kwi141. [DOI] [PubMed] [Google Scholar]
- 2.Anderson RM, May RM. Infectious Diseases of Humans: Dynamics and Control. Oxford: Oxford University Press; 1991. [Google Scholar]
- 3.Pitblado R, Pong R, Irvine A, Nagarajan K, Sahai V. Assessing rural health: Toward developing health indicators for rural Canada. 1999. [Google Scholar]
- 4.Schuman SH. Agromedicine and emerging infectious diseases. J Agromed. 2001;8:19–26. [Google Scholar]
- 5.2001 community profiles. Statistics Canada (Ottawa, ON) 2004. [Google Scholar]
- 6.Mortimer EA, Cherry JD. Pertussis (whooping cough) In: Gershon AA, Hotez PJ, Katz SL, editors. Krugman’s Infectious Diseases of Children. Philadelphia, PA: Mosby; 2004. pp. 443–59. [Google Scholar]
- 7.Tilley PA, Kanchana MV, Knight I, Blondeau J, Antonishyn N, Deneer H. Detection of Bordetella pertussis in a clinical laboratory by culture, polymerase chain reaction, and direct fluorescent antibody staining; accuracy, and cost. Diag Microbiol Infect Dis. 2000;37:17–23. doi: 10.1016/S0732-8893(00)00117-6. [DOI] [PubMed] [Google Scholar]
- 8.Gordis L. Epidemiology. Second Edition. Philadelphia, PA: W.B.: Saunders Company; 2000. Measuring the occurrence of disease; pp. 31–62. [Google Scholar]
- 9.Halperin S, Scheifele D, Barreto L, Pim C, Guasparini R, Medd L, et al. Comparison of a fifth dose of a five-component acellular or a whole cell pertussis vaccine in children four to six years of age. Pediatr Infect Dis J. 1999;21:772–79. doi: 10.1097/00006454-199909000-00006. [DOI] [PubMed] [Google Scholar]
- 10.Pichichero ME, Deloria MA, Rennels MB, Anderson EL, Edwards KM, Decker MD, et al. A safety and immunogenicity comparison of 12 acellular pertussis vaccines and one whole-cell pertussis vaccine given as a fourth dose in 15- to 20-month-old children. Pediatrics. 1997;100:772–88. doi: 10.1542/peds.100.5.772. [DOI] [PubMed] [Google Scholar]
- 11.Langue J, Matisse N, Pacoret P, Undreiner F, Boisnard F, Soubeyrand B, et al. Persistence of antibodies at 5–6 years of age for children who had received a primary series vaccination with a pentavalent whole-cell pertussis vaccine and a first booster with a pentavalent acellular pertussis vaccine: Immunogenicity and tolerance of second booster with a tetravalent acellular vaccine at 5–6 years of age. Vaccine. 2004;22:1406–14. doi: 10.1016/j.vaccine.2003.10.026. [DOI] [PubMed] [Google Scholar]
- 12.Nelson KE, Williams CM, Graham NMH. Infectious Disease Epidemiology. First Edition. 2001. Surveillance; pp. 97–118. [Google Scholar]
- 13.Geisecke J. Modern Infectious Disease Epidemiology. First Edition. London: Arnold; 2002. Routine surveillance of infectious diseases; pp. 148–60. [Google Scholar]
- 14.Kinsley C. Challenges in rural, remote, northern and Aboriginal communities. In: Rural Health in Rural Hands: Strategic Directions for Rural, Remote, Northern and Aboriginal Communities. Ottawa: The Commission, Ministerial Advisory Council on Rural Health: Health Canada; 2002. pp. 9–16. [Google Scholar]
- 15.Stokley S, Smith PJ, Klevens RM, Battaglia MP. Vaccination status of children living in rural areas in the United States: Are they protected? Am J Prev Med. 2001;20(4Suppl):55–60. doi: 10.1016/S0749-3797(01)00280-X. [DOI] [PubMed] [Google Scholar]
- 16.Steyer TE, Mainous A, Geesey ME. The effect of race and residence on the receipt of childhood immunizations: 1993–2001. Vaccine. 2005;23(12):1464–70. doi: 10.1016/j.vaccine.2004.09.019. [DOI] [PubMed] [Google Scholar]
- 17.Skowronski D D, Serres G, MacDonald D, Wu W, Shaw C, Macnabb J, et al. The changing age and seasonal profile of pertussis in Canada. J Infect Dis. 2002;185:1448–53. doi: 10.1086/340280. [DOI] [PubMed] [Google Scholar]
- 18.Broutin H, Rohani P, Guegan JF, Grenfell BT, Simondon F. Loss of immunity to pertussis in a rural community in Senegal. Vaccine. 2004;22:594–96. doi: 10.1016/j.vaccine.2003.07.018. [DOI] [PubMed] [Google Scholar]
- 19.Lacombe K, Yam A, Simondon K, Pinchinat S, Simondon F. Risk factors for acellular and whole-cell pertussis vaccine failure in Senegalese children. Vaccine. 2004;23:623–28. doi: 10.1016/j.vaccine.2004.07.007. [DOI] [PubMed] [Google Scholar]
- 20.Forsyth KD, Campins-Marti M, Caro J, Cherry JD, Greenberg D, Guiso N, et al. New pertussis vaccination strategies beyond infancy: Recommendations by the Global Pertussis Initiative. Clin Infect Dis. 2004;39:1802–9. doi: 10.1086/426020. [DOI] [PubMed] [Google Scholar]
- 21.Simondon F, Preziosi MP, Yam A, Kane CT, Chabirand L, Iteman I, et al. A randomized double-blind trial comparing a two-component acellular to a whole-cell pertussis vaccine in Senegal. Vaccine. 1997;15:1606–12. doi: 10.1016/S0264-410X(97)00100-X. [DOI] [PubMed] [Google Scholar]
- 22.Mooi FR, van Oirschot H, Heuvelman K, van der Heide HG, Gaastra W, Willems RJ. Polymorphism in the Bordetella pertussis virulence factors p.69/pertactin and pertussis toxin in the Netherlands: Temporal trends and evidence for vaccine-driven evolution. Infect Immun. 1998;66:670–75. doi: 10.1128/iai.66.2.670-675.1998. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.van Boven M, de Melker H S J, Kretzschmar M. A model based evaluation of the 1996–7 pertussis epidemic in the Netherlands. Epidemiol Infect. 2001;127:73–85. doi: 10.1017/s0950268801005684. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.Mäkinen J, Mertsola J, Mooi FR, Van Amersfoorth S, Arvilommi H, Viljanen MK, et al. Bordetella pertussis isolates, Finland. Emerg Infect Dis. 2005;11:183–84. doi: 10.3201/eid1101.040632. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.Tsang RS, Lau AK, Sill ML, Halperin SA, Van Caeseele P, Jamieson F, et al. Polymorphisms of the fimbria fim3 gene of Bordetella pertussis strains isolated in Canada. J Clin Microbiol. 2004;42:5364–67. doi: 10.1128/JCM.42.11.5364-5367.2004. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26.Peppler MS, Kuny S, Nevesinjac A, Rogers C, de Moissac YR, Knowles K, et al. Strain variation among Bordetella pertussis isolates from Quebec and Alberta provinces of Canada from 1985 to 1994. J Clin Microbiol. 2003;41(7):3344–47. doi: 10.1128/JCM.41.7.3344-3347.2003. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27.Tsang RS, Sill ML, Martin IE, Jamieson F. Genetic and antigenic analysis of Bordetella pertussis isolates recovered from clinical cases in Ontario, Canada, before and after the introduction of the acellular pertussis vaccine. Can J Microbiol. 2005;51:887–92. doi: 10.1139/w05-079. [DOI] [PubMed] [Google Scholar]
- 28.Bromberg K. Pertussis. In: Hoperich PD, Jordan MC, Ronald AR, editors. Infectious Diseases: A Treatise of Infection Processes. Fifth Edition. Philadelphia, PA: JB Lippincott Company; 1994. pp. 393–97. [Google Scholar]
- 29.Pertussis. Vaccine Preventable Diseases. Public Health Agency of Canada (Winnipeg, MB) 2006. [Google Scholar]
- 30.He Q, Viljanen MK, Nikkari S, Lyytikainen R, Mertsola J. Outcomes of Bordetella pertussis infection in different age groups of an immunized population. J Infect Dis. 1994;170:873–77. doi: 10.1093/infdis/170.4.873. [DOI] [PubMed] [Google Scholar]
- 31.Rosner B. Fundamentals of Biostatistics. Pacific Grove, CA: Duxbury Press; 2000. Hypothesis testing: Person-time data; pp. 677–741. [Google Scholar]