Effectiveness of 2024/25 KP.2 Vaccine Against Outpatient COVID‐19 in Canada

TL;DR

The KP.2 vaccine was moderately effective against outpatient COVID-19 in Canada, with protection waning over time.

Contribution

This study provides real-world evidence of KP.2 vaccine effectiveness against outpatient COVID-19 in Canada during late 2024 to early 2025.

Findings

Vaccination reduced the risk of outpatient COVID-19 by approximately 54%.

Protection was strongest in the first two months post-vaccination.

Effectiveness declined significantly after five months.

Abstract

The Canadian Sentinel Practitioner Surveillance Network used the test‐negative design to assess KP.2 vaccine effectiveness (VE) against medically attended outpatient COVID‐19 between November 2024 and April 2025 among participants ≥ 12 years. Analyses included 5410 controls (19% vaccinated) and 435 COVID‐19 cases (10% vaccinated). Nearly three‐quarters (72%) of contributing case viruses were genetically characterized, with XEC (35%) and KP.3.1.1 (38%) variants most commonly identified. Vaccination reduced COVID‐19 risk by approximately half (54%; 95% CI: 36–68) relative to unvaccinated individuals. VE was greatest during the first 2 months postvaccination, reducing risk by two‐thirds and declining to minimal protection by the fifth month postvaccination.

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