VaccineJul 25, 2026

Effectiveness of JN.1-adapted regular and self-amplifying mRNA COVID-19 vaccines against symptoms in adults 60 and older in Japan, October 2024-April 2025

mRNA Technology Weekly Brief ↗PubMed ↗DOI ↗

Updated Jul 26, 2026

Abstract

Vaccine effectiveness (VE) of combined JN.1-adapted vaccines was 46.7% against symptomatic SARS-CoV-2 infection in adults aged 60 years and older.

Out of 954 episodes analyzed, 273 (28.6%) were confirmed SARS-CoV-2 positive.
VE was 51.6% at 7-90 days and 35.9% at more than 90 days after vaccination.
The JN.1-adapted self-amplifying mRNA vaccine alone showed a VE of 74.5% at 7 days or more.
Results suggest that JN.1-adapted mRNA vaccination may provide protection against symptomatic COVID-19 in older adults.

Simplified

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.

Full Text

Full text is available at the source.

View Full Text ↗

Funding

Competing interests

Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: HM has reported a research collaboration with Meiji Seika Pharma Co., Ltd. and has received research funding. HM also reports participation in Pfizer Inc.-funded research outside this work. AI reports grants from Takeda Pharmaceutical Inc., consulting fees from Pfizer Inc. and Astra Zeneca Inc., and lecture fees from Takeda Pharmaceutical Inc., Shionogi Inc., Janssen Pharma Inc., and Modera Inc. outside this work. KM reports grants from Pfizer Inc., consulting fees from Moderna Inc., and lecture fees from MSD outside this work.

PubMed

Effectiveness of JN.1-adapted regular and self-amplifying mRNA COVID-19 vaccines against symptoms in adults 60 and older in Japan, October 2024-April 2025

Abstract

Full Text

Funding

Competing interests

You found one interesting study. We’ll send the next 7.

What Lands in Your Inbox Each Week:

Recent issues from the mrna technology brief