Introduction: Research on SARS-CoV-2 virus has focused on aspects such as treatment, virology, epidemiology and vaccine development. The efficacy of vaccines against SARS-CoV-2 is important for controlling the pandemic. This study assessed how the immune response is affected by age and gender, and its role in causing inflammation as measured by neutrophil-to-lymphocyte ratio (NLR) in vaccinated patients versus non-vaccinated COVID-19 negative patients. Methodology: A case-control study was done involving 187 randomly selected patients who had undergone laboratory examinations to evaluate the SARS-CoV-2 IgG antibody titer and hematological parameters at 21 to 31 days after the second dose of vaccination. Patients were divided into case and control groups according to their vaccination status. Results: The average age among the cases was 51 ± 13 years whereas the average age among the control group was 47 ± 15 years. In cases where the response to immunization was measured by SARS-CoV-2 IgG antibody, results had a median of 7.7 U/mL characterized by a large variation (p < 0.0001). There was no significant difference based on age (p = 0.451) and gender (p = 0.622) in SARS-CoV-2 IgG antibody titers in patients vaccinated with two doses of Pfizer–BioNTech COVID-19 vaccine. In addition, there was no significant difference in NLR ratio between cases and controls (p = 0.117). Conclusions: Our data showed that there is no inflammation at 21 to 31 days post vaccination with Pfizer-BioNTech COVID-19 vaccine, regardless of age and gender, based on the hematological parameters.