Background: AstraZeneca is the viral vector vaccine. This vaccine has a more advanced method that uses a modified virus to trigger antibodies to fight the Covid-19 virus. Objective: To evaluate the impact of Body Mass Index on the Antibody Titer after AstraZeneca Vaccination atUTA'45 Vaccine Center. Method: Cross-sectional prospective method was used in this study with a convenience sampling design. Only participants who signed the informed consent were included in this study. Results: The results of the P-value on the comparison of Gender and BMI are 0.36 which indicates a correlation between BMI and Gender, also in BMI and age (the P-Value of the comparison of age and BMI was 0.57) BMI plays an important role in the comparison of these factors. BMI is one of the factors that influence the development of antibodies after vaccination. Antibody titer 2 is significantly affected by BMI, the correlation between BMI and antibody titer 2 is very significant ( P-Value 0,000). Conclusion: Based on this study, it was found that there was a correlation between Age, Gender, and BMI on Antibody Titer after AstraZeneca vaccination. However, the correlation between Age and Gender to BMI is not very significant, the presence of factors can still affect Antibody Titers. In addition, it can also be concluded that there is a very significant correlation between antibody titer 2 (post-vaccination antibody titer) and a person's BMI. This is shown from the results of the P-Value of 0.000.