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

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.

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.