Evolution of SARS-CoV-2; The Omicron Variant and its Considerations, A Mini Review

Document Type : Review Article


1 Department of Clinical Pharmacy, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran

2 Department of Clinical Pharmacy, Shahid Faghihi Hospital, Shiraz University of Medical Sciences, Shiraz, Iran



Since the beginning of detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2019, many genetic evolutions of this virus have been reported. The most recent variant that caused the fourth wave of Covid-19 infection worldwide, Omicron, has shown various mutations at its receptor binding domain therefore inducing changes in behavior compared to previous variants. According to published data, major genetic mutations, differences in clinical severity and also resistance to prevention and treatment strategies have been observed. Lower rates of disease severity, hospital and intensive care unit admissions, younger age of contamination with progression to severe disease, resistance to 2 dose vaccination, risk of re-infection and resistance to monoclonal antibodies have been some of the many differences in the recent variant of concern. In the following article some considerations and modifications of the Omicron variant with regard to its general characteristics and treatment will be discussed.
Please cite this article as: Dena Firouzabadi. Evolution of SARS-CoV-2; The Omicron Variant and its Considerations, A Mini Review. Trends in Pharmaceutical Sciences. 2022;8(2):119-126. doi: 10.30476/TIPS.2022.95341.1144


1.    Lewnard JA, Hong VX, Patel MM, Kahn R, Lipsitch M, Tartof SY. Clinical outcomes among patients infected with Omicron (B. 1.1. 529) SARS-CoV-2 variant in southern California. medRxiv. 2022. https://doi.org/10.1101/2022.01.11.22269045
2.    Del Rio C, Omer SB, Malani PN. Winter of Omicron-The Evolving COVID-19 Pandemic. JAMA. 2022 Jan 25;327(4):319-320. doi: 10.1001/jama.2021.24315. PMID: 34935863.
3.    Poudel S, Ishak A, Perez-Fernandez J, Garcia E, León-Figueroa DA, Romaní L, Bonilla-Aldana DK, Rodriguez-Morales AJ. Highly mutated SARS-CoV-2 Omicron variant sparks significant concern among global experts - What is known so far? Travel Med Infect Dis. 2022 Jan-Feb;45:102234. doi: 10.1016/j.tmaid.2021.102234. Epub 2021 Dec 8. PMID: 34896326; PMCID: PMC8666662.
4.    Meena M, Vijayalakshmi A. COVID-19 TO OMICRON-AN OVERVIEW. COVID 19: Impact and Response Volume VII.61.
5.    Fantini J, Yahi N, Colson P, Chahinian H, La Scola B, Raoult D. The puzzling mutational landscape of the SARS‐2‐variant Omicron. J Med Virol. 2022; 94: 2019- 2025. doi:10.1002/jmv.27577
6.    Ettaboina SK, Nakkala K, Laddha K. A Mini Review on SARS-COVID-19-2 Omicron Variant (B. 1.1. 529). SciMed J. 2021;3(4):399-406. doi: 10.28991/SciMedJ-2021-0304-10.
7.    Shuai H, Chan JF, Hu B, Chai Y, Yuen TT, Yin F, et al. Attenuated replication and pathogenicity of SARS-CoV-2 B.1.1.529 Omicron. Nature. 2022 Mar;603(7902):693-699. doi: 10.1038/s41586-022-04442-5. Epub 2022 Jan 21. PMID: 35062016. 
8.    SARS-CoV-2 Viral Mutations: Impact on COVID-19 Tests: U.S. Food & Drug Administration; 2021 [Available from: https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/sars-cov-2-viral-mutations-impact-covid-19-tests#omicronvariantimpact 
9.    Metzger CMJA, Lienhard R, Seth-Smith HMB, Roloff T, Wegner F, Sieber J, Bel M, Greub G, Egli A. PCR performance in the SARS-CoV-2 Omicron variant of concern? Swiss Med Wkly. 2021 Dec 10;151:w30120. doi: 10.4414/smw.2021.w30120. PMID: 34909869.
10.    Lauring AS, Tenforde MW, Chappell JD, Gaglani M, Ginde AA, McNeal T, et al. Clinical Severity and mRNA Vaccine Effectiveness for Omicron, Delta, and Alpha SARS-CoV-2 Variants in the United States: A Prospective Observational Study. medRxiv [Preprint]. 2022 Feb 7:2022.02.06.22270558. doi: 10.1101/2022.02.06.22270558. Update in: BMJ. 2022 Mar 9;376:e069761. PMID: 35169811; PMCID: PMC8845432.
11.    Ward IL, Bermingham C, Ayoubkhani D, Gethings OJ, Pouwels K, Yates T, et al. Risk of COVID-19 related deaths for SARS-CoV-2 Omicron (B. 1.1. 529) compared with Delta (B. 1.617. 2). medRxiv. 2022. https://doi.org/10.1101/2022.02.24.22271466
12.    Li A, Maier A, Carter M, Guan TH. Omicron and S-gene target failure cases in the highest COVID-19 case rate region in Canada-December 2021. J Med Virol. 2022 May;94(5):1784-1786. doi: 10.1002/jmv.27562. Epub 2022 Jan 12. PMID: 34964500; PMCID: PMC9015418.
13.    Classification of omicron (B.1.1.529): SARS-CoV-2 variant of concern: World Health Organization 2021 [updated 2021. Available from: https://www.who.int/news/item/26-11-2021-classification-of-omicron-(b.1.1.529)-sars-cov-2-variant-of-concern.
14.    Tang J, Randolph AG, Novak T, Walker TC, Loftis LL, Zinter MS, Irby K, Khurana S. Systemic and Lower Respiratory Tract Immunity to SARS-CoV-2 Omicron and Variants in Pediatric Severe COVID-19 and Mis-C. Vaccines (Basel). 2022 Feb 10;10(2):270. doi: 10.3390/vaccines10020270. PMID: 35214728; PMCID: PMC8879098.
15.    Wolter N, Jassat W, Walaza S, Welch R, Moultrie H, Groome M, et al. Early assessment of the clinical severity of the SARS-CoV-2 omicron variant in South Africa: a data linkage study. Lancet. 2022 Jan 29;399(10323):437-446. doi: 10.1016/S0140-6736(22)00017-4. Epub 2022 Jan 19. PMID: 35065011; PMCID: PMC8769664.
16.    Ulloa AC, Buchan SA, Daneman N, Brown KA. Early estimates of SARS-CoV-2 Omicron variant severity based on a matched cohort study, Ontario, Canada. MedRxiv. 2021. https://doi.org/10.1101/2021.12.24.21268382
17.    Christie B. Covid-19: Early studies give hope omicron is milder than other variants. BMJ. 2021 Dec 23;375:n3144. doi: 10.1136/bmj.n3144. PMID: 34949600.
18.    Chan, M. HKUMed Finds Omicron SARS-CoV-2 Can Infect Faster and Better Than Delta in Human Bronchus But With Less Severe Infection in Lung. Braz J Implantol Health Sci. 2022, 4, 50-54.
19.    Andrews N, Stowe J, Kirsebom F, Toffa S, Rickeard T, Gallagher E, et al. Covid-19 Vaccine Effectiveness against the Omicron (B.1.1.529) Variant. N Engl J Med. 2022 Apr 21;386(16):1532-1546. doi: 10.1056/NEJMoa2119451. Epub 2022 Mar 2. PMID: 35249272; PMCID: PMC8908811.  
20.    Cele S, Jackson L, Khoury DS, Khan K, Moyo-Gwete T, Tegally H, et al. SARS-CoV-2 Omicron has extensive but incomplete escape of Pfizer BNT162b2 elicited neutralization and requires ACE2 for infection. medRxiv [Preprint]. 2021 Dec 17:2021.12.08.21267417. doi: 10.1101/2021.12.08.21267417. Update in: Nature. 2021 Dec 23;: PMID: 34909788; PMCID: PMC8669855.
21.    Wilhelm A, Widera M, Grikscheit K, Toptan T, Schenk B, Pallas C, et al. Reduced neutralization of SARS-CoV-2 omicron variant by vaccine sera and monoclonal antibodies. MedRxiv. 2021. https://doi.org/10.1101/2021.12.07.21267432
22.    Keeton R, Tincho MB, Ngomti A, Baguma R, Benede N, Suzuki A, et al. T cell responses to SARS-CoV-2 spike cross-recognize Omicron. Nature. 2022 Mar;603(7901):488-492. doi: 10.1038/s41586-022-04460-3. Epub 2022 Jan 31. Erratum in: Nature. 2022 Apr;604(7907):E25. PMID: 35102311; PMCID: PMC8930768.
23.    Kundu R, Narean JS, Wang L, Fenn J, Pillay T, Fernandez ND, et al. Cross-reactive memory T cells associate with protection against SARS-CoV-2 infection in COVID-19 contacts. Nat Commun. 2022;13(1):1-8. doi:10.1038/s41467-021-27674-x
24.    Gottlieb RL, Vaca CE, Paredes R, Mera J, Webb BJ, Perez G, et al. Early Remdesivir to Prevent Progression to Severe Covid-19 in Outpatients. N Engl J Med. 2022 Jan 27;386(4):305-315. doi: 10.1056/NEJMoa2116846. Epub 2021 Dec 22. PMID: 34937145; PMCID: PMC8757570.
25.    Shafer SL, Simoneaux R. Omicron Therapeutics. ASA Monitor. 2022;86(2):21-37. https://doi.org/10.1097/01.asm.0000820396.70292.ef
26.    Li P, Wang Y, Lavrijsen M, Lamers MM, de Vries AC, Rottier RJ, et al. SARS-CoV-2 Omicron variant is highly sensitive to molnupiravir, nirmatrelvir, and the combination. Cell Res. 2022 Mar;32(3):322-324. doi: 10.1038/s41422-022-00618-w. Epub 2022 Jan 20. PMID: 35058606; PMCID: PMC8771185.
27.    Lingas G, Luciani L, Cochin M, Villarroel P, Moureau G, Petit P, et al. Activity of Tixagevimab/Cilgavimab against the Omicron variant of SARS-CoV-2 in a hamster model. 2022. https://doi.org/10.21203/rs.3.rs-1399448/v1
28.    Aggarwal A, Stella AO, Walker G, Akerman A, Milogiannakis V, Hoppe AC, et al. SARS-CoV-2 Omicron: reduction of potent humoral responses and resistance to clinical immunotherapeutics relative to viral variants of concern. medRxiv. 2021. https://doi.org/10.1101/2021.12.14.21267772
29.    Fang FF, Shi PY. Omicron: a drug developer's perspective. Emerg Microbes Infect. 2022 Dec;11(1):208-211. doi: 10.1080/22221751.2021.2023330. PMID: 34951568; PMCID: PMC8741250.
30.    Westendorf K, Žentelis S, Wang L, Foster D, Vaillancourt P, Wiggin M, et al. LY-CoV1404 (bebtelovimab) potently neutralizes SARS-CoV-2 variants. bioRxiv [Preprint]. 2022 Mar 24:2021.04.30.442182. doi: 10.1101/2021.04.30.442182. Update in: Cell Rep. 2022 Apr 25;:110812. PMID: 33972947; PMCID: PMC8109210.
31.    Bojkova D, Widera M, Ciesek S, Wass MN, Michaelis M, Cinatl J. Reduced interferon antagonism but similar drug sensitivity in Omicron variant compared to Delta variant of SARS-CoV-2 isolates. Cell Res. 2022:32;319-321. doi: 10.1038/s41422-022-00619-9 
32.    Coronavirus Disease 2019 (COVID-19) Treatment Guidelines 2022 [Available from: https://www.covid19treatmentguidelines.nih.gov/.