Leah J RicketsonShannon N PyraJames D Kellner2024-11-202024-11-202024-11-26https://hdl.handle.net/1880/120066Poster presented at 2024 Canadian Immunization Conference, Ottawa, November 26-28, 2024Invasive pneumococcal disease in the later years of the COVID-19 pandemic in Calgary, Canada: 2022-2023 Ricketson, LJ, Kellner, JD Background: Pneumococcal conjugate vaccines were introduced in 2002 (PCV7) and 2010 (PCV13) in Alberta. IPD declined during the COVID-19 pandemic in Calgary then increased following reduction of non-pharmaceutical interventions (NPIs). Methods: The Calgary area Streptococcus pneumoniae Epidemiology Research (CASPER) team conducts population-based surveillance on all IPD cases presenting to Calgary and area health facilities. Here we examine the changes in incidence per 3-month periods (quarters) during the early pandemic years 2020-2021 and the late-pandemic years 2022-2023 for all ages combined. Results: Late 2022 incidence increased to above pre-PCV levels. January to June 2023 had an average incidence of 4 cases per 100,000 people per quarter, which is above the average incidence of 2.5 in the same two quarters of the late-PCV13 years: 2017-2019 (IRR: 1.5, 95%CI: 1.0-2.2, P=0.0382). By Oct-Dec 2023 incidence remained above late PCV13-era levels (IRR: 1.5, 95%CI: 1.02-2.1, P=0.0317). In 2023, PCV serotypes 4 (18.9%), 9V (12.3%), 7F (9.9%), and 3 (9.9%) were most common. The rise of ST9V is notable as this was a relatively uncommon serotype in Calgary after the introduction of PCVs. Childhood vaccine rates in Calgary declined slightly, but not significantly during the COVID-19 era. Conclusions: With the reduction of NPIs, IPD increased in 2022 to above levels seen in the late-PCV era and this continued into 2023. By the end of 2023 IPD incidence remained above late vaccine-era levels. This is likely associated with increases in antecedent viral infections, particularly influenza and RSV, as childhood vaccine rates remained stable. The most common serotypes in 2023 are serotypes found in PCV13, as well as the new PCV15 and PCV20 vaccines. PCV13 serotypes persist, especially in adults and some are on the rise despite universal PCV13 use in children. This highlights the need for more effective direct protection for adults through vaccination.enStreptococcus pneumoniaePneumococcusInvasive pneumococcal diseaseCOVID--19 PandemicIncidenceEpidemiologyPresentation