not-yet-known not-yet-known not-yet-known unknown We estimated XBB.1.5 vaccine effectiveness (VE) against symptomatic SARS-CoV-2 infection among adults aged ≥65 years during the 2023/24 JN.1 lineage-predominant period in a European multi-country test-negative case-control study at primary care level. We estimated VE adjusted by study site, age, sex, chronic conditions and onset date. We included 220 cases and 1733 controls. The VE was 48% (95% CI: 12–71), 23% (95% CI: -11–48) and 5% (95% CI: -92–56) among those with symptom onset 1–5 , 6–11, and ≥12 weeks after vaccination, respectively. XBB.1.5 vaccine provided short and moderate protection against JN.1 symptomatic infection.

We conducted a multicentre test-negative case-control study covering the period from October 2023 to January 2024 among adult patients aged ≥18 years hospitalised with severe acute respiratory infection in Europe. We provide early estimates of the effectiveness of the newly adapted XBB.1.5 COVID-19 vaccines against PCR-confirmed SARS-CoV-2 hospitalisation. Vaccine effectiveness was 48% overall, ranging between 68% at 14–29 days and 40% at 60–105 days post vaccination. The adapted XBB.1.5 COVID-19 vaccines conferred protection against COVID-19 hospitalisation in the first 3.5 months post vaccination, with VE >70% in older adults (≥65 years) up to 1 month post vaccination.