Objective: COVID-19 survivors are either vaccinated or not usually afraid of COVID-19 side effects. This study aims to investigate post Covid-19 biochemical changes among healthy and chronically diseased either vaccinated or not subjects.  Material and Method: 144 patients (72 males and 72 females) previously (two years ago) diagnosed with SARS-CoV-2 contagion by RT-PCR were enrolled as cohort group of this research. Major biochemical alterations of post Covid-19 infection among healthy, diabetic and heart-diseased Egyptian males and females either vaccinated or not were examined. Result and discussion: Results revealed that COVID-19 infection caused antioxidant levels to decrease significantly (p≤0.05) in association with a significant increase in oxidative lipid peroxidation initiating inflammation leading to deterioration of organ function (liver, heart and kidney) associated with biochemical alterations in glucose and lipid metabolism with improper immunoglobulin level. Conclusion: Chronic diseased patients were more affected by post-COVID-19 biochemical alterations. Vaccination attenuated post-COVID-19 biochemical changes. The study is expected to motivate previously infected people to check their health status and not vaccinated people to take the appropriate vaccine.