Study identification

EU PAS number

EUPAS1000000481

Study ID

1000000481

Official title and acronym

Brand-specific influenza vaccine effectiveness in the Nordic countries

DARWIN EU® study

No

Study countries

Denmark
Finland
Sweden

Study description

Seasonal influenza is a major public health concern, particularly for older adults and high-risk individuals. While vaccination is the primary preventive measure, its effectiveness varies across seasons, virus subtypes, and populations. This study evaluates the brand-specific effectiveness of seasonal influenza vaccines during the 2024–2025 season in Denmark, Finland, and Sweden, leveraging Nordic health registries for near real-time, large-scale assessments. The study focuses on individuals aged 65 years and older and high-risk adults under 65, estimating influenza vaccine effectiveness (IVE) against laboratory-confirmed influenza, influenza-like illness, hospitalization, ICU admission, and mortality. The objective is to provide timely brand-specific IVE estimates to inform vaccination strategies.

A nationwide register-based matched cohort design was used, applying target trial emulation and additional methodologies such as test-negative case-control design, negative control outcome analyses, regression discontinuity, and prior event rate adjustments to enhance validity. A feasibility assessment confirms that Denmark and Finland provide comprehensive data, while Sweden has partial regional coverage. The assessment finds that Nordic health registries, combined with appropriate methodologies, provide a strong foundation for conducting timely brand-specific IVE studies to support vaccination policy and regulatory decision-making.

This study generates high-quality real-world evidence to guide public health strategies ahead of the 2025–2026 influenza season. By leveraging robust data infrastructure and advanced epidemiological methods, it strengthens evidence-based vaccine policy and preparedness for future influenza seasons.

Study status

Finalised
Research institutions and networks

Institutions

Swedish Medical Products Agency

Contact details

Anders Hviid 0000-0002-7509-9127

Primary lead investigator
ORCID number:
0000-0002-7509-9127

Study timelines

Date when funding contract was signed

Planned:
Actual:

Study start date

Planned:
Actual:

Date of interim report, if expected

Planned:
Actual:

Date of final study report

Planned:
Actual:
Sources of funding
EMA
Regulatory

Was the study required by a regulatory body?

Yes

Is the study required by a Risk Management Plan (RMP)?

Not applicable