Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 52 12 2023 11 28 2621 2629 EN Akram Sadat Ahmadi Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Nazanin Zahra Shafiei–Jandaghi Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Kaveh Sadeghi Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Ahmad Nejati Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Sevrin Zadheidar Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Talat Mokhtari-Azad Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Jila Yavarian 1. Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran 2. Research Center for Antibiotic Stewardship and Antimicrobial Resistance, Tehran University of Medical Sciences, Tehran, Iran 2022 12 28 2023 08 13 Background: Whole viral genome sequencing with next generation sequencing (NGS) technique is useful tool for determining the diversity of variants and mutations of severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2). In this study we have attempted to characterize the mutations and circulating variants of the SARS-CoV-2 genome during the 4th wave of COVID-19 pandemic in Tehran, Iran in 2021. Methods: We performed complete genome sequencing of 15 SARS-CoV-2 detected from 15 COVID-19 patients during the 4th wave of COVID-19 pandemic with NGS. Three groups of the patients at the beginning, middle and the end of the 4th wave were compared together. Results: We detected alpha and delta variants during the 4th wave of the pandemic. The results illustrated a dominance of amino acid substitution D614G in spike, and the most frequent mutants were N­-R203K, G204R, S235F, nsp12-P323L, nsp6-G106del, G107del and F108del. Conclusion: The detection of the virus mutations is a useful procedure for identifying the virus behavior and its genetic evolution in order to improve the efficacy of the monitoring strategies and therapeutic measures. https://ijph.tums.ac.ir/index.php/ijph/article/view/30768 https://ijph.tums.ac.ir/index.php/ijph/article/download/30768/8115