This cohort study sponsored by Assiut University aims to assess the prevalence and severity of COVID-19 infections in individuals who have received at least one dose of a registered COVID-19 vaccine in Egypt. Given the ongoing global pandemic and the emergence of variants, understanding breakthrough infections is critical for vaccine manufacturers and public health authorities. The findings could influence vaccine development strategies, booster shot recommendations, and public health policies. The study's outcomes may also provide insights into the effectiveness of various vaccines in real-world settings, potentially impacting market positioning for vaccine developers. The competitive landscape includes major vaccine manufacturers such as Pfizer, Moderna, AstraZeneca, and Sinovac, all of whom are closely monitoring breakthrough infection rates to adapt their strategies.