Tehran University of Medical Sciences Immunology and Genetics Journal 2645-4831 5 3 2022 09 22 119 127 Soroush Khojasteh-Kaffash Student Research Committee, School of Medicine, Birjand University of Medical Sciences, Birjand, Iran Reza Jafari Department of Basic Sciences, School of Medicine, Shahroud University of Medical Sciences. Shahroud, Iran Alireza Fereidouni Student Research Committee, School of Allied Medicine, Birjand University of Medical Sciences, Birjand, Iran Ali Fanoodi Student Research Committee, School of Medicine, Birjand University of Medical Sciences, Birjand, Iran Vajehallah Raeesi Department of Internal Medicine, School of Medicine, Birjand University of Medical Sciences, Birjand, Iran Mahsa Najafzadeh Student Research Committee, School of Medicine, Birjand University of Medical Sciences, Birjand, Iran Mohammad Fereidouni Cellular and Molecular Research Center, Birjand University of Medical Sciences, Birjand, Iran 2023 05 01 2024 06 22 Background/objectives: Studies have shown that immune responses to COVID-19 vaccines are impaired in dialysis patients which may affect immunity to vaccines. Therefore, this study aimed to evaluate SARS-COV-2 neutralizing antibodies in hemodialysis patients for 2 and 6 weeks after receiving inactivated Sinopharm vaccine. Methods: In this study, 172 people were divided into two groups. The first group included 108 hemodialysis patients, while the second group included 64 health workers as a control group. In order to evaluate SARS-COV-2 neutralizing antibodies titers, the peripheral blood samples were collected from all participants 2 and 6 weeks after receiving the second dose of Sinopharm vaccine. Samples were centrifuged and the neutralizing antibody against receptor-binding domain (RBD) was determined using the indirect ELISA technique. Results: Hemodialysis patients had lower titers of IgG neutralizing antibodies compared to the control group (P <0.001). The titers of SARS-COV-2 neutralizing antibodies were not significantly different at 2 weeks in comparison with 6 weeks after vaccination (P=0.9204). Our findings showed a significant increase in titers of IgG neutralizing antibodies after vaccination in people with a history of COVID-19 (P=0.002). The seropositivity rate for neutralizing antibodies against RBD was significantly different between seropositive (immune) and seronegative (non-immune) patients 6 weeks after vaccination (P=0.022). Conclusions: The titers of neutralizing antibodies against SARS-COV-2 were lower in hemodialysis patients than in healthy individuals. This is probably due to the poor immune system. However, patients who received two doses of inactivated Sinopharm vaccine showed a higher antibody titer 6 weeks after vaccination. https://igj.tums.ac.ir/index.php/igj/article/view/130 https://igj.tums.ac.ir/index.php/igj/article/download/130/106