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Abstract

BACKGROUND

The Canadian Sentinel Practitioner Surveillance Network routinely undertakes multiplex respiratory virus testing, vaccine effectiveness (VE) estimation by test-negative design (TND), and whole genome sequencing (WGS) of vaccine-targeted viruses.

AIM

To estimate 2025/26 LP.8.1 VE against community-based COVID-19, including variant-specific, and explore the impact of other respiratory viruses among COVID-19 cases and/or controls.

METHODS

Participants were ≥ 12-year-old outpatients presenting with acute respiratory illness between 26 October 2025 and 07 March 2026. COVID-19 vaccination information was registry-based. Primary TND analyses excluded influenza virus-infected controls. Sensitivity analyses explored inclusion and/or exclusion of influenza and other respiratory viral infections among COVID-19 cases and/or controls. WGS supported VE interpretation and variant-specific estimation.

RESULTS

We included 3,802 participants (2,832 (74%) aged 12–64 years; 970 (26%) aged ≥ 65 years), with 310 COVID-19 cases (29 vaccinated; 9%) and 3,492 controls (577 vaccinated; 17%). At median 9 weeks post-vaccination, LP.8.1 VE was 48% (95%CI: 21 to 66): 44% (95%CI: −12 to 72) for 12–64 and 53% (95%CI: 21 to 73) for ≥ 65-year-olds. In sensitivity analyses, VE was stable for ≥ 65-year-olds. Among 12–64-year-olds, VE decreased when including influenza virus infections among controls but increased when excluding co-infections, recognising uncertainty with reduced sample size. Against viruses that failed vs succeeded WGS, VE was 26% (95%CI: −63 to 66) vs 53% (95%CI: 24 to 71), 63% (95%CI: 30 to 80) against the XFG variant. Most SARS-CoV-2 co-infections with semi-quantification, including those failing WGS, showed higher viral load for the non-SARS-CoV-2 infection.

CONCLUSION

The 2025/26 LP.8.1 vaccine approximately halved the medically attended COVID-19 risk. Multiplex testing to identify primary co-infections among cases, or correlated vaccine-preventable infections among controls, may address VE under-estimation.

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This work is licensed under a Creative Commons Attribution 4.0 International License.
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2026-05-07
2026-06-10
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Interim 2025/26 LP.8.1 vaccine effectiveness estimates against COVID-19 from the Canadian Sentinel Practitioner Surveillance Network (SPSN): insights into possible impact of influenza and other respiratory virus co-circulation
<p class="citation"> <span>Citation style for this article:</span> <span class="meta-value authors"> <a href="/search?value1=Danuta+M+Skowronski&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Skowronski Danuta M</a>, <a href="/search?value1=Yuping+Zhan&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Zhan Yuping</a>, <a href="/search?value1=Samantha+E+Kaweski&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Kaweski Samantha E</a>, <a href="/search?value1=Michelle+B.+Cox&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Cox Michelle B.</a>, <a href="/search?value1=Lea+Separovic&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Separovic Lea</a>, <a href="/search?value1=Sara+Carazo&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Carazo Sara</a>, <a href="/search?value1=Romy+Olsha&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Olsha Romy</a>, <a href="/search?value1=Katie+Dover&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Dover Katie</a>, <a href="/search?value1=Suzana+Sabaiduc&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Sabaiduc Suzana</a>, <a href="/search?value1=Christine+Lacroix&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Lacroix Christine</a>, <a href="/search?value1=Richard+G+Mather&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Mather Richard G</a>, <a href="/search?value1=Maan+Hasso&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Hasso Maan</a>, <a href="/search?value1=In%C3%A8s+Levade&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Levade Inès</a>, <a href="/search?value1=Agatha+N+Jassem&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Jassem Agatha N</a>, <a href="/search?value1=Isabelle+Meunier&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Meunier Isabelle</a>, <a href="/search?value1=Ruimin+Gao&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Gao Ruimin</a>, <a href="/search?value1=Nathalie+Bastien&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Bastien Nathalie</a></span>. Interim 2025/26 LP.8.1 vaccine effectiveness estimates against COVID-19 from the Canadian Sentinel Practitioner Surveillance Network (SPSN): insights into possible impact of influenza and other respiratory virus co-circulation. <a href="/content/ecdc">Euro Surveill.</a> 2026;31(18):pii=2600331. <a href="https://doi.org/10.2807/1560-7917.ES.2026.31.18.2600331" title="doi link" target="_blank">https://doi.org/10.2807/1560-7917.ES.2026.31.18.2600331</a> <span class="ES_Article_citation"> <span class="generated">Received</span>: 13 Apr 2026;&nbsp;&nbsp; <span class="generated">Accepted</span>: 30 Apr 2026 </span> </p>
/content/10.2807/1560-7917.ES.2026.31.18.2600331
/content/10.2807/1560-7917.ES.2026.31.18.2600331
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