The high emergency in the control of the pandemic has determined that the scientific community is dedicated to the production of effective vaccines for immunization against SARS-CoV-2. With the emergence of new variants of SARS-CoV-2, there was a need to increase immunity in the vaccinated population through a booster dose. The booster dose is allowed to increase the immunity of individuals and, consequently, reduce the probability of reinfection, as well as severe symptoms associated with COVID-19. Objective: To evaluate the acquired immunity to COVID-19 through vaccination, and to verify the influence of the booster dose on the antibody’s concentration. Materials and Methods: Data were collected from 965 individuals of both genders and vaccinated for COVID-19. Results: 91.8% of the sample had neutralizing antibodies against SARS-CoV-2, and the group of fully vaccinated individuals had a higher percentage of neutralized antibodies compared to individuals who did not have a booster dose (53.2% vs. 38 .7%). Discussion: Neutralizing antibodies were found in 91.8% of the sample, which demonstrates the effectiveness of vaccination in the production of antibodies. The results demonstrated the effectiveness of the booster dose in the production of neutralizing antibodies against SARS-CoV-2. Conclusion: Vaccination was quite effective in producing neutralizing antibodies. In addition, booster vaccination increased humoral immunity.