2705. Serotype Replacement Following Childhood Pneumococcal Conjugate Vaccination Programs in British Columbia, Canada

Abstract

Background: Pneumococcal conjugate vaccines have substantially reduced the incidence of invasive pneumococcal disease (IPD); however, the impact of the vaccine on non-vaccine serotypes (NVT) remains unclear. We evaluated the effect of PCV13 use in British Columbia, Canada. Methods: The annual incidence following implementation of PCV7 (September 2004), and PCV13 (September 2010) was calculated using provincial laboratory surveillance data. We also compared incidence rate ratios (IRR) against pre-PCV13 (2004-10) and pre-PCV7 (2002-03) baselines using Poisson regression for non-conjugate vaccine type IPD. Results: A total of 4,490 cases were reported over the 14 year period. The overall annual incidence increased from 5.73 cases per 100,000 population in 2002 to 7.90 cases per 100,000 population in 2015. Compared with baseline, PCV7 reduced VT-IPD (IRR: 0.49; 95% CI: 0.42-0.56), but the additional 6 serotypes in the PCV13 vaccine caused 214% increase in IPD (IRR: 2.65; 95% CI: 2.12-3.39). The majority of this increase is related to an increase in NVT disease (IRR: 3.17; 95% CI: 2.62-3.87) such as 23B, 23A, 9N, 20, 33F, 15C, 17F and 6C. IPD from PCV13 vaccine serotypes 19A and 7F which emerged after PCV7 continue to be high. Conclusion: The introduction of PCV13 has a modest impact on IPD rates, due to inadequate control of serotypes 19A and 7F, and, of concern, IPD rates continue to escalate due to serotype replacement by non-vaccine serotypes.