Stephanie L Hughes1, Jeffrey C Kwong1,2,3,4, Kevin L Schwartz1,2,4, Cynthia Chen1,4, Caitlin Johnson1, Ye Li1,2, Alex Marchand-Austin1, Shelly Bolotin1,2,5, Frances B Jamieson1,5, Steven J Drews6,7, Margaret L Russell8, Lawrence W Svenson8,9,10,11, Salaheddin M Mahmud12, Natasha S Crowcroft13. 1. Public Health Ontario, Toronto, ON, Canada. 2. Dalla Lana School of Public Health, University of Toronto, Toronto, ON, M5T 3M7, Canada. 3. Department of Family & Community Medicine, University of Toronto, Toronto, ON, Canada. 4. ICES, Toronto, ON, Canada. 5. Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada. 6. Canadian Blood Services, Ottawa, ON, Canada. 7. Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB, Canada. 8. Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada. 9. Alberta Health, Edmonton, AB, Canada. 10. Division of Preventive Medicine, University of Alberta, Edmonton, AB, Canada. 11. School of Public Health, University of Alberta, Edmonton, AB, Canada. 12. Vaccine and Drug Evaluation Centre, Max Rady College of Medicine, University of Manitoba, Winnipeg, MB, Canada. 13. Dalla Lana School of Public Health, University of Toronto, Toronto, ON, M5T 3M7, Canada. natasha.crowcroft@utoronto.ca.
Abstract
OBJECTIVES: Although pertussis vaccines have been widely used for many decades, a burden of illness persists. Resurgences in Ontario, Canada, have not been substantial in the past decade, but an outbreak of pertussis occurred in Toronto between 1 October 2005 and 31 March 2006. Previous Ontario studies found high vaccine effectiveness (VE) in the initial years post-immunization. In order to explore the impact of outbreaks and external factors on VE, we investigated pertussis VE during the period 2006-2008. METHODS: We assessed pertussis VE using a frequency-matched case-control study for the period 1 March 2006 to 31 December 2008. We used logistic regression to estimate VE by age, time since last vaccination, and vaccination status according to the Ontario recommended schedule. We compared analyses including and excluding cases from Toronto, and to two recent Ontario pertussis VE studies. RESULTS: We included 1797 confirmed cases and 7188 matched controls. Most cases were under 4 years of age during the study period. Pertussis VE was 3.8% (95% CI: - 21.0, 24.0) in the period 15-364 days following the last pertussis vaccine dose, and increased with increasing time since vaccination. Pertussis VE in the first 15-364 days excluding Toronto increased to 57.1% (95% CI: 26.0, 75.1), but the trend of increasing VE with time since vaccination persisted. Although VE was higher in older (6-11 years) than younger (0-5 years) children, it was lower at 12-13 years than after 14 years. CONCLUSION: VE was lower in comparison with other studies conducted in Ontario, particularly in younger children. Various factors occurring during the study period may have influenced the results, including clinical testing of asymptomatic contacts, laboratory testing and methods and reporting practice, and a sensitive case definition. Further studies are needed to optimize methods for measuring VE to inform pertussis vaccine policy.
OBJECTIVES: Although pertussis vaccines have been widely used for many decades, a burden of illness persists. Resurgences in Ontario, Canada, have not been substantial in the past decade, but an outbreak of pertussis occurred in Toronto between 1 October 2005 and 31 March 2006. Previous Ontario studies found high vaccine effectiveness (VE) in the initial years post-immunization. In order to explore the impact of outbreaks and external factors on VE, we investigated pertussis VE during the period 2006-2008. METHODS: We assessed pertussis VE using a frequency-matched case-control study for the period 1 March 2006 to 31 December 2008. We used logistic regression to estimate VE by age, time since last vaccination, and vaccination status according to the Ontario recommended schedule. We compared analyses including and excluding cases from Toronto, and to two recent Ontario pertussis VE studies. RESULTS: We included 1797 confirmed cases and 7188 matched controls. Most cases were under 4 years of age during the study period. Pertussis VE was 3.8% (95% CI: - 21.0, 24.0) in the period 15-364 days following the last pertussis vaccine dose, and increased with increasing time since vaccination. Pertussis VE in the first 15-364 days excluding Toronto increased to 57.1% (95% CI: 26.0, 75.1), but the trend of increasing VE with time since vaccination persisted. Although VE was higher in older (6-11 years) than younger (0-5 years) children, it was lower at 12-13 years than after 14 years. CONCLUSION: VE was lower in comparison with other studies conducted in Ontario, particularly in younger children. Various factors occurring during the study period may have influenced the results, including clinical testing of asymptomatic contacts, laboratory testing and methods and reporting practice, and a sensitive case definition. Further studies are needed to optimize methods for measuring VE to inform pertussis vaccine policy.
Authors: Valerie Waters; Frances Jamieson; Susan E Richardson; Michael Finkelstein; Anne Wormsbecker; Scott A Halperin Journal: Pediatr Infect Dis J Date: 2009-07 Impact factor: 2.129
Authors: David N Fisman; Patrick Tang; Tanya Hauck; Susan Richardson; Steven J Drews; Donald E Low; Frances Jamieson Journal: BMC Public Health Date: 2011-09-07 Impact factor: 3.295
Authors: Natasha S Crowcroft; Caitlin Johnson; Cynthia Chen; Ye Li; Alex Marchand-Austin; Shelly Bolotin; Kevin Schwartz; Shelley L Deeks; Frances Jamieson; Steven Drews; Margaret L Russell; Lawrence W Svenson; Kimberley Simmonds; Salaheddin M Mahmud; Jeffrey C Kwong Journal: PLoS One Date: 2018-05-02 Impact factor: 3.240