NCT07279766

Effectiveness of mRNA-1273 Variant-Containing Vaccine Formulation Against Severe Outcomes in Adults Aged 50-64 Years Without Risk Factors for Severe COVID-19

A Phase 4 Pragmatic, Randomized Trial to Evaluate the Effectiveness of mRNA-1273 Variant-Containing Vaccine Formulation Against Severe Outcomes in Adults Aged 50-64 Years Without Risk Factors for Severe COVID-19

• Status: Active Not Recruiting
• Phase: Phase 4
• Study type: Interventional
• Enrollment: 285,000 (estimated)
• Sponsor: Tor Biering-Sørensen · Academic / Other
• Sex: All
• Age: 50 Years – 64 Years
• Healthy volunteers: Accepted

Summary

The purpose of this pragmatic randomized trial is to evaluate the vaccine effectiveness of the COVID-19 vaccine, mRNA-1273, in adults aged 50-64 years without known risk factors for severe COVID-19 infection. Participants will be randomized 1:1 to either COVID-19 vaccine or no COVID-19 vaccine.

Detailed description

The study is a pragmatic, registry-based, open-label, individually randomized trial. The Danish nationwide administrative health registries will be used for data collection including baseline information, follow-up data, and safety monitoring. The study aims to randomize a total of 285,000 participants. Participants will be individually randomized 1:1 to receive either a COVID-19 vaccine or no COVID-19 vaccine. The study is designed to assess the vaccine effectiveness of the COVID-19 vaccine vs. no COVID-19 vaccine on the risk of medically attended COVID-19 infection.

Conditions

• COVID-19

Interventions

Type	Name	Description
BIOLOGICAL	mRNA-1273 (Moderna COVID-19 vaccine)	For this arm, the current variant formulation of Spikevax (mRNA-1273) vaccine will be used.

Timeline

• Start date: 2025-12-11
• Primary completion: 2026-08-01
• Completion: 2026-08-01
• First posted: 2025-12-12
• Last updated: 2026-03-16

Locations

2 sites across 1 country: Denmark