However, in all countries and regions around the world, there are people who elect not to receive the COVID-19 vaccines for various reasons. They are a naturally occurring control group, as opposed to the vaccinated population (i.e. the experimental group). Indeed, the whole COVID-19 vaccine campaigns can be regarded as the unprecedented largest human clinical trials on vaccine safety, by design or not, as the vaccines' long term safety data was not available when they were provided to people under EUA. Then, the unvaccinated population in different parts of the world are very unique large control groups in such a global clinical trial. Due to the highly valuable health data of this unvaccinated population, between October 2021 and February 2022, a UK-based organization called Control Group Cooperative (CGC) independently collected their self-reported data on their health status, reasons for declining to receive the COVID-19 vaccines, whether they have been infected by the SARS-Co