Invasive Pneumococcal Disease Epidemiology and Conjugate Vaccines in Canada, 2000-2019

Invasive pneumococcal disease (IPD) remains a significant burden despite implementation of pneumococcal conjugate vaccines (PCVs) in childhood immunization programs.

To analyze IPD epidemiology in Canada following 7-valent pneumococcal conjugate vaccine (PCV7) and 13-valent PCV (PCV13) introductions and evaluate the potential outcomes associated with newer vaccines, such as PCV15, PCV20, and PCV21.

This cross-sectional study included IPD isolates from children and adults with IPD across Canada from January 1, 2000, to December 31, 2019. Cases were identified through bacterial isolates sent to national reference laboratories. Data were analyzed from January 2022 to January 2026.

Introduction of PCV7 and PCV13.

IPD incidence rates and proportion analyses were calculated for serotypes belonging to PCV7, PCV13, PCV15, PCV20, and PCV21 using Statistics Canada population estimates. PCV7 and PCV13 impact was assessed using generalized linear piecewise quasi-Poisson regression models.

A total of 37 921 IPD isolates were analyzed. Age data were available for 37 591 isolates (17.9% children aged <18 years; 82.1% adults aged ≥18 years), and sex data for 35 303 isolates (51.5% male; 41.6% female). Following PCV7 introduction, PCV7-specific serotype IPD rates decreased by 98.5%, from an incidence rate (IR) of 20.1 (95% CI, 17.8-22.6) in year 0 to 0.31 (95% CI, 1.0-0.5) in year 7 (P < .001), in children younger than 5 years (direct cohort) and 76.3%, from an IR of 2.2 (95% CI, 1.6-3.0) in year 0 to (0.5; 95% CI, 0.3-0.9) in year 7, in individuals aged 10 years or older (indirect cohort), although the difference was not statistically significant (P = .74). After PCV13 introduction, PCV13-only serotype IPD rates decreased by 90.6% in the direct cohort, from an IR of 10.3 (95% CI, 8.812.1) in year 0 to 1.0 (95% CI, 0.65-1.44) in year 9 (P = .03), and 57.1% in the indirect cohort, from an IR of 3.8 (95% CI, 3.1 to 4.6) in year 0 to 1.6 (95% CI, 1.2 to 2.1) in year 9 (P = .001). Vaccine serotypes 3, 4, and 19F persisted, with increases observed in adults aged 18 to 49 years and 50 to 64 years for serotypes 3 and 4, and in adults aged 65 years and older for serotype 19F. Serotype 19A cases declined after introduction of PCV13, with the highest incidence in adults aged 65 years and older. From 2015 to 2019, the potential serotype coverages by PCV15, PCV20, and PCV21 were estimated at 23% to 29%, 32% to 39%, and 36% to 49%, respectively, while nonvaccine types accounted for 45% to 52%.

This cross-sectional study of IPD isolates in Canada found that despite initial IPD reductions following PCVs, IPD in Canada increased, driven by emerging nonvaccine types and persistence of some vaccine serotypes. Indirect protection was limited, particularly among older adults, highlighting the need for direct adult vaccination strategies. These findings suggest that while PCV15, PCV20, and PCV21 may improve serotype coverage, continued development of broader-spectrum vaccines is essential to further reduce IPD burden.