This clinical trial is focused on studying the effects of the time of day when the influenza vaccine is given to adults aged 60 to 85 years. The study will use two different vaccines: Vaxigrip Tetra and Influvac Tetra, both of which are designed to protect against the flu. These vaccines are given as an injection into the muscle and contain inactivated parts of the flu virus, which means they cannot cause the flu but help the body build protection against it.
The main goal of the study is to see how the timing of the vaccine affects the body’s immune response, specifically the level of antibodies, which are proteins that help fight infections. Participants will receive the vaccine at different times of the day, and their antibody levels will be measured 28 days after vaccination. The study will also look at other factors, such as the participants’ natural sleep-wake patterns, known as chronotype, and the occurrence of flu-like symptoms over a six-month period.
Participants will be randomly assigned a time to receive their vaccine and will be monitored for changes in their immune response. The study aims to provide insights into whether the time of day can influence the effectiveness of the flu vaccine, potentially leading to improved vaccination strategies for older adults. The study is expected to conclude by May 2025.



The Netherlands