Background: While protective immunity against some viruses, such as coronaviruses, is relatively short-lived, healing from acute infections of many different viruses, such as those caused by yellow fever, polio, measles, and smallpox, can give cell-mediated and humoral immunity for a lifetime. The main element in the long-term prevention of reinfection by most viruses might be due to the specific antibodies generated by plasma cells. Aim: This study aims to estimate the levels of SARS-CoV-2 Anti-Spike S1 RBD IgM, IgA, and IgG in serum among people in Baghdad after one month of receiving the Pfizer-BioNTech vaccine, infected with the SARS-CoV-2 virus after vaccination and COVID-19 infected patients respectively. Methods: A total of 120 volunteers were enrolled in this study, which was conducted between the 1st of November 2022 and the 13th of January 2023, and they were divided into four groups, each group containing 30 individuals. The study groups were categorized after one month into vaccinated with the Pfizer-BioNTech vaccine (BNT162b2), infected with SARS-CoV-2 after Pfizer vaccination, COVID-19 patients, and control. Results: The study presented a significant difference where (P value < 0.05) in the serum levels of Anti-Spike S1 RBD IgM, IgA, and IgG for all groups compared to the control. Serum levels of S1 RBD IgM Anti-Spike of SARS-CoV-2 in all groups were significantly increased (P value >0.05) compared to each other. For Anti-Spike S1 RBD IgA and IgG, there was no significant difference (P value >0.05) between the COVID-19-infected patients group and those infected by SARS-CoV-2 after the Pfizer vaccination group. Positive correlations were found among Anti-Spike S1 RBD IgM, IgA, and IgG levels in the serum. Conclusions: Natural infection by SARS-CoV-2 or vaccination with Pfizer-BioNTech (BNT162b2) provides significant humoral Immunological protection.