Burden of pertussis and associated complications among adults in Ontario, Canada

Summary

Client: Sanofi Winthrop Industrie S.A

Project ID: P2022-151/ 2025 0980 004 000

Research Question/Objectives: Pertussis (whooping cough) is a highly contagious respiratory infection caused by Bordetella pertussis and is a vaccine-preventable disease. However, vaccine induced protection nor natural immunity is not lifelong. The incidence of pertussis is significantly higher among infants (less than one year of age); however, recent data show that the incidence of pertussis among adolescents and older patients has been increasing over time. Data on risk factors for pertussis among adults is scarce. However, recent studies have shown that adolescents and adults with pre-existing chronic conditions such as asthma, COPD, or obesity may be at higher risk for pertussis. Additionally, immunodeficiency and smoking appear to be associated with worsened pertussis symptoms and an increased pertussis-related hospitalization rate. The goal of this analysis is to describe the overall burden of pertussis and pertussis-related complications in the general Ontario adult patient population and among high-risk patients including patients with respiratory conditions and older adults.

Objectives:
Primary objectives:

1. To document the incidence and severity of pertussis in Ontario among individuals 18 years and older over the period 2004-2019
   a. Estimate the annual incidence of diagnosed pertussis and pertussis with complications stratified by age (18-44, 45-64, 65 years and older)
   b. Estimate the mean age-specific incidence of diagnosed pertussis and pertussis with complications over the study period
   c. Document the prevalence of asthma, COPD, asthma and COPD (ACOS), diabetes mellitus I/II, cardiovascular disease, immunocompromising condition, and neurological disorders among diagnosed pertussis cases and pertussis with complications stratified by age over the study period

Secondary objectives:

1. To describe and compare the pertussis laboratory confirmation request rate in Ontario among individuals 18 years and older with asthma, COPD, ACOS or none, stratified by age over the study period
2. To describe and compare the pertussis vaccination rates (Tdap overall) in Ontario over the study period among individuals 18 years and older stratified by age
   a. Among patients with asthma vs patients without asthma or COPD
   b. Among patients with COPD vs patients without asthma or COPD
   c. Among patients with ACOS vs patients without asthma or COPD
3. To describe and compare the incidence of pertussis, and pertussis with complications in Ontario over the study period among:
   a. Patients with asthma vs patients without asthma or COPD
   b. Patients with COPD vs patients without asthma or COPD
   c. Patients with ACOS vs patients without asthma and COPD
4. To describe chronic condition- and age-related risk factors for pertussis and for pertussis with complications in Ontario among individuals 18 years and older over the study period using a case-control design
5. To describe and compare by age group the risk of severe exacerbation associated with a pertussis episode among Ontario individuals 18 years and older using a self-controlled case series design among
   a. Patients with asthma
   b. Patients with COPD
   c. Patients with ACOS
6. To describe and compare pertussis-related and all-cause Healthcare Resource Utilization (HcRU) (ED visits, and hospitalizations) associated with pertussis diagnosis in asthma, COPD, asthma and COPD (ACOS) patients vs. adults without asthma or COPD, and by age
7. To describe risk of pertussis by pertussis vaccination status and pertussis testing among:
   a. Patients with asthma vs. patients without asthma
   b. Patients with COPD vs. patients without COPD
   c. Patients with ACOS vs. patients with neither COPD nor asthma
8. To describe and compare measures of frailty and serious health events (CV, hospitalizations) before and after a pertussis infection among adults 65 and older

Status: In progress