This study investigates adverse effects and newly diagnosed illnesses following COVID-19 vaccination with Covishield and Covaxin in 267 participants across India. Conducted via an online survey from June 1 to July 5, 2024, the study includes participants of all ages and genders who received at least one dose. Adults aged 20–30 reported the most side effects, which decreased after the second dose. Common short-term side effects were pain, redness, and allergic reactions, while long-term effects included pain, breath shortness, and memory loss, particularly in older adults. Covaxin was linked to more pain and allergies, whereas Covishield was associated with gastrointestinal, liver, and blood-related illnesses. Newly diagnosed illnesses like heart, respiratory, neurological, and kidney-related issues were more common with Covaxin. The study underscores the importance of continuous monitoring and tailored care to manage adverse effects, enhancing public confidence in vaccination programs.