Test-adjusted estimation for pertussis incidence in greater Toronto, Canada, 1993-2006

Area of Science:

• * Epidemiology and Public Health
• * Infectious Disease Dynamics
• * Vaccinology

Background:

• * Pertussis (whooping cough) remains a significant public health issue, disproportionately affecting young children.
• * The actual burden of pertussis in older children and adults is underestimated due to lower testing rates in these demographics.

Purpose of the Study:

• * To characterize the true incidence and burden of pertussis across different age groups.
• * To estimate underdiagnosed pertussis cases using a novel statistical adjustment method.
• * To inform pertussis vaccine booster policy based on transmission dynamics.

Main Methods:

• * Analysis of pertussis testing and case data from the Greater Toronto Area (1993-2006).
• * Application of a meta-regression-based method to adjust for age and sex-specific testing rates.
• * Estimation of case counts assuming uniform testing rates across all demographic groups.

Main Results:

• * Unadjusted data showed highest pertussis incidence in infants (<1 year), declining with age.
• * After test adjustment, the 2-4-year age group exhibited the highest relative incidence (IRR: 5.503).
• * Estimated underdiagnosed cases were highest in 2-4-year-old males and 10-19-year-old females.

Conclusions:

• * Pertussis is significantly underdiagnosed in older children and adults, particularly preschoolers and the elderly.
• * These underdiagnosed populations may be crucial reservoirs for sustaining pertussis transmission.
• * Findings highlight the need to reconsider pertussis vaccine booster strategies for broader age groups.