Strain selection
Exact strain matching is not essential; broad, lineage-level updates may protect populations more reliably.
In brief: must a COVID-19 vaccine exactly match the circulating strain?
No. Evidence reviewed by CTI indicates that vaccines targeting closely related variants can provide comparable real-world protection. Broader lineage-level updates may therefore be more reliable than attempting precise strain matching.
Exact strain matching is not essential for public-health benefit
Evidence from recent seasons shows that vaccines targeting closely related variants have delivered similar real-world effectiveness, even when the specific targeted strain was no longer dominant by peak circulation (Sharff et al., 2025).
For example, vaccines targeting JN.1- and KP.2-lineage variants showed comparable protection despite rapid changes in circulating strains (Sharff et al., 2025; Laniece Delaunay et al., 2025).
Broad, lineage-level updates that prioritise cross-protection, rather than precise strain matching, may therefore offer more robust and reliable population-level protection.
Sources
- Sharff KA, Haslam A, Nealon J. COVID-19 vaccine variant target: how should we choose? Vaccine. 2025;68:127917.
- Laniece Delaunay C, et al. COVID-19 Vaccine Effectiveness Among Target Groups in Europe, Oct 2024–Jan 2025, VEBIS Primary Care Network. Influenza and Other Respiratory Viruses. 2025;19(11):e70120.
Figures and citations migrated verbatim from the CTI evidence pages; interactive charts can be added at implementation.
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