ArticleVaccines2025
Early and Late Influenza Vaccine Effectiveness in South Korea During the 2023-2024 Season.
Article in Vaccines, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 4 papers.
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Who cites it
4 citing papers in PubMed.
- Influenza Vaccine Effectiveness in Korea: A Systematic Review and Meta-Analysis of Real-World Evidence from the Past Decade.Vaccines · 2026Review
- Article
- Interim Vaccine Effectiveness Against Influenza and Hospitalization, Republic of Korea, 2024-2025 (HIMM Network).Vaccines · 2025Article
- Influenza vaccine effectiveness among adults aged ≥60 years in northeastern Zhejiang Province, China, 2021-2024.Frontiers in public health · 2025Article
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Authors and funding
14 authors.
Funding
Abstract
backgroundDuring the 2023-2024 season, the influenza epidemic in South Korea peaked earlier, and the influenza vaccination rate among individuals aged ≥ 65 was high (82.2%). However, data on real-world vaccine effectiveness against influenza are lacking.
methodsFrom November 2023 to April 2024, we conducted a multicenter retrospective case-control study on adult patients aged ≥ 18 years who presented with influenza-like illness at seven medical centers as a part of a hospital-based influenza morbidity and mortality surveillance (HIMM) program in South Korea. Demographic and clinical data were collected from questionnaire surveys and electronic medical records. Using a test-negative design, we assessed the effectiveness of the 2023-2024 seasonal influenza vaccine, with age, sex, and comorbidities included as covariates.
resultsA total of 3390 participants were enrolled through the HIMM system, including 1695 patients with either rapid antigen test (RAT) or real-time reverse-transcription polymerase chain reaction (RT-PCR) positive results and controls matched for age, sex, and months of registration. Among the 1696 influenza-positive patients, 1584 (93.5%) underwent RAT, with 88.9% testing positive for influenza A and 11.1% for influenza B. During the study periods, the overall vaccine effectiveness (VE) was 24.3% (95% confidence interval (CI), 11.5 to 35.2). The VE was insignificant when limited to older adults aged ≥ 65 years (13.5%; 95% CI, -17.9 to 36.6). In the subgroup analysis by subtype, the VE was 19.0% (95% CI, 5.0 to 31.0) for influenza A and 56.3% (95% CI, 35.3 to 70.6) for influenza B. Notably, influenza VE was 20.4% (95% CI, 2.9 to 34.8) in the early period (November to December) but decreased to 12.4% (95% CI, -14.9 to 33.2) in the late period (January to April).
conclusionDuring the 2023-2024 season, the influenza vaccine showed a modest effectiveness (24.3%) against laboratory-confirmed influenza, which was particularly higher for influenza B. Because the VE was insignificant in older adults, particularly during the late period, better immunogenic influenza vaccines with longer-lasting protection should be considered.
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