SARS-CoV-2 S1-RBD IgG and IL-6 serum level reduction after 120 days (4 months) of the second dose of Pfizer–BioNTech vaccine administration to the medical students in the University of Diyala

Abstract

Background: SARS-CoV-2 mRNA vaccines such as Pfizer–BioNTech have confirmed a high efficiency; however, there is a limitation of data existence about the duration of immune responses and their relation to age and side effects. The aim of this study is to estimate the SARS-CoV-2 S1-RBD IgG level after 30 days (1 month) and 120 days (4 months) of the second dose of Pfizer–BioNTech vaccine administered to the medical students of the University of Diyala. Methods: The study was conducted after the approval of the Medical College of Al-Iraqia University, the Medical College of the University of Diyala, and the Iraqi Ministry of Health. We selected 45 students from the Medical College of the University of Diyala randomly who were fully vaccinated (two doses of Pfizer–BioNTech vaccine, 0.5 ml of the vaccine for each dose), and they agreed to give 5 ml of their blood twice (after 1 month and 4 months), which was carried out in the Higher Education Laboratory inside the Medical College, University of Diyala. The period of sample collection was 5 months (from September 2021 until February 2022). A serological analysis to measure SARS-CoV-2 S1-RBD IgG was done by using Diasino, SARS-CoV-2 S1-RBD IgG ELISA Kit, China, which was carried out in the Higher Education Laboratory, inside the Medical College, University of Diyala. Demographic data were taken from the study participants (age and gender). The same individuals of the study were divided into two groups according to the time frame (1 month and 4 months) after the second dose of the Pfizer–BioNTech vaccine administration. For statistical analysis, we used SPSS version 26 and STATISTICA version 12 to input, check, and analyze data. For qualitative variables, standard approaches of frequencies and percentages were used, whereas for quantitative variables, mean and standard deviation were used. A P-value of less than 0.05 was considered as significant for SARS CoV-2 S1-RBD IgG plasma levels. Results: The study found that the male–female ratio was 17.8: 82.2, and the mean of the age of the vaccinated students was 20.977 years. The serum quantities of SARS-CoV-2 S1-RBD IgG and IL-6 levels post second dose of the Pfizer–BioNTech vaccine after 30 days (1 month) and 120 days (4 months) were shown to be statistically non-parametric. Using the independent two-sample Mann–Whitney test, a significant difference (P < 0.05) was observed for SARS-CoV-2 S1-RBD IgG and IL-6 levels between 120 days (4 months) after the second dose of the Pfizer–BioNTech vaccine and 30 days (1 month). Conclusion: SARS-CoV-2 S1-RBD IgG and IL-6 levels decreased significantly after 120 days (4 months) of the second dose of Pfizer–BioNTech vaccination.