This clinical trial is focused on understanding the immune response to SARS-CoV-2, the virus responsible for COVID-19, in people with weakened immune systems. The study involves healthy individuals and those who are immunocompromised, such as nursing home residents, dialysis patients, and kidney and lung transplant patients, aged 18 to 105. The trial will use two different vaccines: Comirnaty Omicron XBB.1.5 and Comirnaty JN.1, both of which are mRNA vaccines designed to protect against specific variants of the virus.

The purpose of the study is to assess the level of antibodies, which are proteins in the blood that help fight infections, against the most common variant of the virus. This will be done three times a year. The study will also look at how well the vaccines work in creating a strong immune response, which includes both the quality of the antibody response and the cellular immune response, which involves other parts of the immune system that help protect against infections.

Participants in the study will receive the vaccines through an injection. The study will take place over several years, from 2023 to 2026, to gather comprehensive data on how the immune system responds over time. This information will help improve understanding of vaccine effectiveness in people with different health conditions and contribute to better protection strategies against COVID-19.