Publication date: Jul 25, 2026
In Japan, JN. 1-adapted conventional mRNA and self-amplifying mRNA (sa-mRNA) COVID-19 vaccines were introduced during the 2024-2025 season. We estimated the effectiveness of these vaccines against symptomatic SARS-CoV-2 infection among adults aged ≥60 years using a test-negative design (October 1, 2024-April 30, 2025). Eligible episodes were ≥1 COVID-19-like symptom and SARS-CoV-2 testing. Vaccine effectiveness (VE) was estimated using mixed-effects logistic regression. We included 954 episodes; 273 (28. 6%) were SARS-CoV-2-positive. VE of combined JN. 1-adapted conventional and self-amplifying mRNA vaccines was 46. 7% (95% CI: 5. 5-69. 9) at ≥7 days, 51. 6% (95% CI: 5. 0-75. 4) at 7-90 days, and 35. 9% (95% CI: -50. 0-72. 6) at >90 days after vaccination. VE of the JN. 1-adapted sa-mRNA vaccine alone was 74. 5% (95% CI: 31. 3-90. 6) at ≥7 days. JN. 1-adapted mRNA vaccination, including the sa-mRNA vaccine, was estimated to provide protection against symptomatic SARS-CoV-2 infection among older adults in Japan.
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| Concepts | Keywords |
|---|---|
| April | COVID-19 |
| Japan | Japan |
| Vaccine | JN.1 |
| mRNA | |
| Self-amplifying | |
| Vaccine effectiveness |
Semantics
| Type | Source | Name |
|---|---|---|
| disease | MESH | SARS-CoV-2 infection |
| pathway | REACTOME | SARS-CoV-2 Infection |
| disease | MESH | included |