Introduction: The Coronavirus Disease-2019 (COVID-19) pandemic, being an emerging world health issue, has led to the swift development of vaccines. Various lifestyles, health conditions, and behaviours affect the body’s reaction to immunisation. Aim: To evaluate the association of Adverse Effects Following Immunisation (AEFI) with different lifestyles and health patterns. Materials and Methods: A cross-sectional online epidemiological analytical survey in study population across India was carried out in Mumbai, India, from 1st June 2021 to 21st June 2021, using Google form survey. It included a sample of 586 responders. A questionnaire consisting of 26 questions regarding lifestyle habits and AEFIs following COVID-19 vaccine administration was distributed. Questions about lifestyle were obtained using Simple Lifestyle Indicator Questionnaire (SLIQ) which includes questions regarding diet, activity/exercise, alcohol consumption, smoking, and stress. Association between the SLIQ score and number and duration of AEFI was determined. Measurement data was presented as means with standard deviation. The SLIQ scores and age were compared between the different groups (AEFI present/absent, no. of AEFI, duration of AEFI) using one-way analysis of variance (ANOVA). Results: The incidence of reported AEFI was n=577 (76.4%). The most frequently reported AEFI was redness, n=328 (74.38%) followed by pain, n=233 (52.83%), swelling n=233 (52.83%) and fever n=222 (50.34%). It was observed that those with a higher SLIQ score, had an increased number and duration of AEFI (p=0.001, ANOVA). With increase in age, number and duration of AEFI experienced decreased (p<0.0001, ANOVA). Conclusion: Balanced diet, mild to moderate exercise, abstinence from smoking and alcohol, reduced stress and younger age increase the number of AEFI, indicating a robust immune response.