Background: Severe acute respiratory syndrome coronavirus 2 immunoglobulin G (SARS-CoV-2-IgG) antibodies have been widely used to assist clinical diagnosis and occupational exposure risks. Objectives: This study aimed to estimate SARS-CoV-2 IgG levels acquired due to different vaccination schemes. Materials and methods: A retrospective study was performed on volunteers from the Instituto Politécnico de Lisboa. Blood samples were collected and analyzed through the ELISA methodology and a statistical analysis was conducted. Results: Among study participants, the percentage of women was higher than men, with an average age of 39.02 years. 88.5% of individuals had an mRNA vaccination versus 11.5% for a viral vector vaccination. Moderna vaccine had the highest IgG titer (9.62 index), while the lowest titer was 5.97 index, obtained by the Janssen vaccine. Data from individuals with the 2nd vaccine dose corresponded to the highest percentage of seropositive titers (62.6%). Regarding the time between vaccination and sample collection, 41.9% were collected over six months and 2.2% between 1 and 2 months. Discussion: Data demonstrated that the vaccine technology, the period between vaccination and collection, and cross-vaccination have a significant impact on SARS-CoV-2 IgG levels. In conclusion, future assessment of individual immune responses and group immunity is crucial for occupational exposure and public health.