Background: Vaccination is considered to be the most significant kind of control over the pandemic. Currently, the in-use Pfizer vaccine is considered to be the most effective prevention method to control this pandemic. Aim: Our study aims to estimate serum levels of interleukin-10 in fully vaccinated students with the Pfizer/ BioNTech vaccine after one month and four months. Methodology: 90 Samples were randomly taken from two different groups of students from Al-Iraqia University, who were Pfizer-BioNTech completely vaccinated. A 5 ml was drawn from 45 volunteered students after 1 month of vaccination and the other 45 after 4 months of complete vaccination. Serological analysis was carried out for measuring interleukin-10 of human serum by using the Human Interleukin-10 ELISA Kit. Demographic data were also collected from participants including age and gender. Results: The serum levels of Human Interleukin-10 after 2^nd dose of the Pfizer/BioNTech vaccine have significantly dropped in four months (P<0.05) compared with one month of administration. Conclusion: Human Interleukin-10 serum levels significantly decreased in the 4^th month of the 2^nd dose of the Pfizer-BioNTech vaccine.