Introduction
Extensive research on the SARS-CoV-2 virus and its related disease has been conducted with the aim of more familiarity with structural and genetic characteristics, origin, evolution, genomic changes, and pathological function. Despite many efforts to combat COVID-19, the disease is still not fully controllable, and at any moment, the emergence of a potential variant with new mutations can weaken vaccines and herd immunity through vaccinations to combat the virus [1]. In this study, while presenting general information about the origin and evolution of coronaviruses, information related to mutations and their possible effect on transmissibility, the severity of pathogenicity, interaction with the host and vaccine effectiveness, molecular characteristics, epidemiology, and the location of the emergence of coronaviruses with the centrality of the five variants of concern alpha (B.1.1.7), beta (B.1.351), gamma (P.1), delta (B.1.617.2) and omicron (B.1.1.529) are presented to be used to better understand and choose effective diagnostic and therapeutic solutions.

Materials and Methods
In this systematic review, we tried to use the information available in articles, databases, and various servers, such as World Health Organization (WHO), CDC, NCBI, GISAID, ViPR, GitHub, Nextstrain, Pango lineages, and other genomic data sources according to the latest updates on coronaviruses, especially the new types of SARS-CoV-2 [4]. For genomic analysis, first, the complete genome sequence of the coronaviruses HCoV-229E (NC002645.1), HCoV-NL63 (NC005831.2), HCoV-HKU1 (NC006577.2), HCoV-OC43 (NC006213.1), SARS-CoV BJ01 (AY278488.2), SARS-CoV Tor2 (AY274119.3), Bat-SL CoVZC45 (MG772933.1), Bat-SL CoVZXC21 (MG772934.1), Bat-CoV RaTG13 (MN996532.2), MERS-CoV (NC019843.3), SARS-CoV-2 Wuhan-Hu-1 (NC045512.2) and 5 variants of concern B.1.1.7 (MW633953.1), B.1.351 (MW598413.1), P‌.1 (MW642250.1), B.1.617.2 (MZ009823.1) and B.1.1.529 (OL672836.1) with accession numbers obtained from GenBank or GISAID, were retrieved and saved from databases, such as NCBI and ViPR in FASTA format. Sequence alignment was performed by Workbench CLC Main software (Bioinformatics, CA, USA) and then the phylogenetic tree was drawn by the Neighbour-Join method with 1000 repetitions (bootstrap) by MEGA X software. To display the tree more clearly, FigTree v1.4.4 was assisted. The genomic sequence of Wuhan-Hu-1 was also considered a reference variant to study genetic diversity.

Results
The two phenomena of mutation and recombination in coronaviruses have led to the emergence of new variants with the interspecies transmission, adaptability to new hosts, high prevalence, and greater virulence severity [11]. More up-to-date variants have a large number of mutations in their spike gene, many of them in the RBD and NTD, which play a key role in ACE-2 binding and antibody recognition. S:‌D614G is associated with viral loads in the upper respiratory tract and the age of patients. S:N501Y plays a role in the effective connection between spike and ACE2 receptor.



S:H69- and S:V70- will announce the negative results of the S assay in TaqPath tests, which can be a useful proxy for disease prevalence known as the S gene target failure phenomenon or SGTF. S:N679K and S:P681H near the furin cleavage site facilitate spike cleavage into two S1 and S2 domains and thus increase fusion and viral infection [25]. Also, S:K417N and S:E484A are associated with immune escape. Using amino acid interaction networks (AAI), the effect of mutations can be investigated and the ability and extent of different variants to escape against antibodies can be shown [63]. mRNA-1273 (Moderna), BNT162b2 (Pfizer–BioNTech), and Ad26.COV2.S (Janssen) are three highly effective vaccines against the epidemic, although booster vaccination is more effective against delta and omicron variants [65]. Nevertheless, it should be admitted that unexpected mutations and the emergence of new types have made planning and certainty in decisions almost impossible.




Discussion
Currently, COVID-19 is the most important public health challenge worldwide. Extensive studies based on structural, genomic, and functional comparisons between SARS-CoV-2 and other similar coronaviruses and variants of this new virus have been carried out to reveal the origin of emergence, behavior, and spread pattern of the virus to obtain important information [62]. The occurrence of mutations and continuous evolution has led to the rapid and simultaneous emergence of different variants, each of these changes can contribute to the escape of therapeutic methods, such as neutralizing antibodies (Nab) and convalescent plasma, as well as reducing the effectiveness of vaccines. Detailed analysis of the similarities and differences of viruses reported in different regions of the world using sequencing, determination of amino acid interaction networks (AAI), as well as the examination of their biological cycle and pathological function, can be of great help in adopting more accurate strategies with higher efficiency in recognition, control, and treatment of such emerging diseases [63]. Therefore, regular and accurate study of the genetic diversity of the virus in any country or geographical region can provide valuable information that these changes will somehow correspond to the virulent power and the rate of virus spread. These data are also useful for vaccine production and the prescription of appropriate drugs. As a result, all countries should cooperate with the World Health Organization to prevent the spread of such variants, so that they monitor genetic and antigenic changes in the global virus population and at the same time conduct experiments to clarify the phenotypic effects of mutations. On the other hand, effective vaccines that target important new strains, such as XBB and BQ.1 should be provided, at least technically, and platforms should be prepared for updating vaccines.

Ethical Considerations

Compliance with ethical guidelines
Ethical principles in writing this article have been observed in accordance with the guidelines of the National Ethics Committee and the Committee on Publication Ethics (COPE).

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.
Authors' contributions
All authors equally contributed to preparing this article.

Conflicts of interest
The authors declare no conflict of interest.

Acknowledgements
The author of the article expresses his gratitude to the Vice Chancellor for Research and Technology of The University of Tabriz.

 

1. Guo S, Liu K, Zheng J. The genetic variant of SARS-CoV-2: Would it matter for controlling the devastating pandemic? Int J Biol Sci. 2021; 17(6):1476-85. [DOI:10.7150/ijbs.59137] [PMID] [PMCID]
2. Zheng J. SARS-CoV-2: An emerging coronavirus that causes a global threat. Int J Biol Sci. 2020; 16(10):1678-85. [DOI:10.7150/ijbs.45053] [PMID] [PMCID]
3. Bi K, Herrera-Diestra JL, Bai Y, Du Z, Wang L, Gibson G, et al. The risk of SARS-CoV-2 Omicron variant emergence in low and middle-income countries (LMICs). Epidemics. 2023; 42:100660. [DOI:10.1016/j.epidem.2022.100660] [PMID] [PMCID]
4. Harvey WT, Carabelli AM, Jackson B, Gupta RK, Thomson EC, Harrison EM, et al. SARS-CoV-2 variants, spike mutations and immune escape. Nat Rev Microbiol. 2021; 19(7):409-24. [DOI:10.1038/s41579-021-00573-0] [PMID] [PMCID]
5. Dudas G, Carvalho LM, Rambaut A, Bedford T. MERS-CoV spillover at the camel-human interface. Elife. 2018; 7:e31257. [DOI:10.7554/eLife.31257] [PMID] [PMCID]
6. Araf Y, Akter F, Tang Yd, Fatemi R, Parvez MSA, Zheng C, et al. Omicron variant of SARS-CoV-2: Genomics, transmissibility, and responses to current COVID-19 vaccines.J Med Virol. 2022; 94(5):1825-32. [DOI:10.1002/jmv.27588] [PMID] [PMCID]
7. Chen J, Lu H. New challenges to fighting COVID-19: Virus variants, potential vaccines, and development of antivirals. Biosci Trends. 2021; 15(2):126-8. [DOI:10.5582/bst.2021.01092] [PMID]
8. Fauver JR, Petrone ME, Hodcroft EB, Shioda K, Ehrlich HY, Watts AG, et al. Coast-to-coast spread of SARS-CoV-2 during the early epidemic in the United States. Cell. 2020; 181(5):990-6.e5. [DOI:10.1016/j.cell.2020.04.021] [PMID] [PMCID]
9. Meredith LW, Hamilton WL, Warne B, Houldcroft CJ, Hosmillo M, Jahun AS, et al. Rapid implementation of SARS-CoV-2 sequencing to investigate cases of health-care associated COVID-19: A prospective genomic surveillance study. Lancet Infect Dis. 2020; 20(11):1263-71. [DOI:10.1016/S1473-3099(20)30562-4] [PMID]
10. Lau SKP, Wong EYM, Tsang CC, Ahmed SS, Au-Yeung RKH, Yuen KY, et al. Discovery and sequence analysis of four deltacoronaviruses from birds in the Middle East reveal interspecies jumping with recombination as a potential mechanism for avian-to-avian and avian-to-mammalian transmission. J Virol. 2018; 92(15):e00265-18. [DOI:10.1128/JVI.00265-18] [PMID] [PMCID]
11. Hu B, Zeng LP, Yang XL, Ge XY, Zhang W, Li B, et al. Discovery of a rich gene pool of bat SARS-related coronaviruses provides new insights into the origin of SARS coronavirus. PLoS Pathog. 2017; 13(11):e1006698. [DOI:10.1371/journal.ppat.1006698] [PMID] [PMCID]
12. Cele S, Gazy I, Jackson L, Hwa SH, Tegally H, Lustig G,  et al. Escape of SARS-CoV-2 501Y. V2 from neutralization by convalescent plasma. Nature. 2021; 593(7857):142-6. [DOI:10.1038/s41586-021-03471-w] [PMID] [PMCID]
13. Sui J, Aird DR, Tamin A, Murakami A, Yan M, Yammanuru A, et al. Broadening of neutralization activity to directly block a dominant antibody-driven SARS-coronavirus evolution pathway. PLoS Pathog. 2008; 4(11):e1000197. [DOI:10.1371/journal.ppat.1000197] [PMID] [PMCID]
14. Woo PC, Lau SK, Lam CS, Tsang AK, Hui SW, Fan RY,  et al. Discovery of a novel bottlenose dolphin coronavirus reveals a distinct species of marine mammal coronavirus in Gammacoronavirus. J Virol. 2014; 88(2):1318-31. [DOI:10.1128/JVI.02351-13] [PMID] [PMCID]
15. Wu F, Zhao S, Yu B, Chen YM, Wang W, Song ZG, et al. A new coronavirus associated with human respiratory disease in China. Nature. 2020; 579(7798):265-9. [DOI:10.1038/s41586-020-2008-3] [PMID] [PMCID]
16. Chen Y, Liu Q, Guo D. Emerging coronaviruses: Genome structure, replication, and pathogenesis. J Med Virol. 2020; 92(4):418-23. [DOI:10.1002/jmv.25681] [PMID] [PMCID]
17. Chan JF, To KK, Tse H, Jin DY, Yuen KY. Interspecies transmission and emergence of novel viruses: Lessons from bats and birds. Trends Microbiol. 2013; 21(10):544-55. [DOI:10.1016/j.tim.2013.05.005] [PMID] [PMCID]
18. Kaur N, Singh R, Dar Z, Bijarnia RK, Dhingra N, Kaur T. Genetic comparison among various coronavirus strains for the identification of potential vaccine targets of SARS-CoV2. Infect Genet Evol. 2021; 89:104490. [DOI:10.1016/j.meegid.2020.104490] [PMID] [PMCID]
19. Lu R, Zhao X, Li J, Niu P, Yang B, Wu H, et al. Genomic characterisation and epidemiology of 2019 novel coronavirus: Implications for virus origins and receptor binding. Lancet. 2020; 395(10224):565-74. [DOI:10.1016/S0140-6736(20)30251-8] [PMID]
20. Xu J, Zhao S, Teng T, Abdalla AE, Zhu W, Xie L, et al. Systematic comparison of two animal-to-human transmitted human coronaviruses: SARS-CoV-2 and SARS-CoV. Viruses. 2020; 12(2):244. [DOI:10.3390/v12020244] [PMID] [PMCID]
21. Walls AC, Park YJ, Tortorici MA, Wall A, McGuire AT, Veesler D. Structure, function, and antigenicity of the SARS-CoV-2 spike glycoprotein. Cell. 2020; 181(2):281-92. e6. [DOI:10.1016/j.cell.2020.02.058] [PMID] [PMCID]
22. Wrapp D, Wang N, Corbett KS, Goldsmith JA, Hsieh CL, Abiona O, et al. Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation. Science. 2020; 367(6483):1260-3. [DOI:10.1126/science.abb2507] [PMID] [PMCID]
23. Vankadari N, Wilce JA. Emerging WuHan (COVID-19) coronavirus: Glycan shield and structure prediction of spike glycoprotein and its interaction with human CD26. Emerg Microbes Infect. 2020; 9(1):601-4. [DOI:10.1080/22221751.2020.1739565] [PMID] [PMCID]
24. Public Health England. Investigation of novel SARS-CoV-2 variant: Variant of concern 202012/01. London: Public Health England Briefing; 2020. [Link]
25. Davies NG, Abbott S, Barnard RC, Jarvis CI, Kucharski AJ, Munday JD, et al. Estimated transmissibility and impact of SARS-CoV-2 lineage B. 1.1. 7 in England. Science. 2021; 372(6538):eabg3055. [DOI:10.1126/science.abg3055] [PMID] [PMCID]
26. Starr TN, Greaney AJ, Hilton SK, Ellis D, Crawford KHD, Dingens AS, et al. Deep mutational scanning of SARS-CoV-2 receptor binding domain reveals constraints on folding and ACE2 binding. Cell. 2020; 182(5):1295-310. e20. [DOI:10.1016/j.cell.2020.08.012] [PMID] [PMCID]
27. Young BE, Fong S-W, Chan YH, Mak TM, Ang LW, Anderson DE, et al. Effects of a major deletion in the SARS-CoV-2 genome on the severity of infection and the inflammatory response: An observational cohort study. Lancet. 2020; 396(10251):603-11. [DOI:10.1016/S0140-6736(20)31757-8] [PMID]
28. Greaney AJ, Loes AN, Crawford KHD, Starr TN, Malone KD, Chu HY, et al. Comprehensive mapping of mutations in the SARS-CoV-2 receptor-binding domain that affect recognition by polyclonal human plasma antibodies. Cell Host Microbe. 2021; 29(3):463-76. e6. [DOI:10.1016/j.chom.2021.02.003] [PMID] [PMCID]
29. Tegally H, Wilkinson E, Giovanetti M, Iranzadeh A, Fonseca V, Giandhari J, et al. Detection of a SARS-CoV-2 variant of concern in South Africa. Nature. 2021; 592(7854):438-43. [DOI:10.1038/s41586-021-03402-9] [PMID]
30. Choi JY, Smith DM. SARS-CoV-2 variants of concern.Yonsei Med J. 2021; 62(11):961-8. [DOI:10.3349/ymj.2021.62.11.961] [PMID] [PMCID]
31. Ramanathan M, Ferguson ID, Miao W, Khavari PA. SARS-CoV-2 B. 1.1. 7 and B. 1.351 spike variants bind human ACE2 with increased affinity. Lancet Infect Dis. 2021; 21(8):1070. [DOI:10.1016/S1473-3099(21)00262-0] [PMID]
32. Amanat F, Thapa M, Lei T, Ahmed SMS, Adelsberg DC, Carreno JM, et al. The plasmablast response to SARS-CoV-2 mRNA vaccination is dominated by non-neutralizing antibodies and targets both the NTD and the RBD. medRxiv. 2021. [preprint]. [DOI:10.1101/2021.03.07.21253098]
33. Faria NR, Mellan TA, Whittaker C, Claro IM, Candido DDS, Mishra S, et al. Genomics and epidemiology of a novel SARS-CoV-2 lineage in Manaus, Brazil. Science. 2021; 372(6544):815-21. [PMID]
34. Naveca FG, Nascimento V, de Souza VC, Corado AL, Nascimento F, Silva G, et al. COVID-19 in Amazonas, Brazil, was driven by the persistence of endemic lineages and P. 1 emergence. Nat Med. 2021; 27(7):1230-8. [DOI:10.1038/s41591-021-01378-7] [PMID]
35. Sabino EC, Buss LF, Carvalho MPS, Prete CA Jr, Crispim MAE, Fraiji NA, et al. Resurgence of COVID-19 in Manaus, Brazil, despite high seroprevalence. Lancet. 2021; 397(10273):452-5. [DOI:10.1016/S0140-6736(21)00183-5] [PMID]
36. Yadav PD, Sapkal GN, Abraham P, Ella R, Deshpande G, Patil DY, et al. Neutralization of variant under investigation B. 1.617. 1 with sera of BBV152 vaccinees. Clin Infect Dis. 2022; 74(2):366-8. [DOI:10.1093/cid/ciab411] [PMID]
37. Sarkale P, Patil S, Yadav PD, Nyayanit DA, Sapkal G, Baradkar S, et al. First isolation of SARS-CoV-2 from clinical samples in India. Indian J Med Res. 2020; 151(2-3):244-50. [DOI:10.4103/ijmr.IJMR_1029_20] [PMID] [PMCID]
38. Cherian S, Potdar V, Jadhav S, Yadav P, Gupta N, Das M, et al. SARS-CoV-2 spike mutations, L452R, T478K, E484Q and P681R, in the second wave of COVID-19 in Maharashtra, India. Microorganisms. 2021; 9(7):1542. [DOI:10.3390/microorganisms9071542] [PMID] [PMCID]
39. Shiehzadegan S, Alaghemand N, Fox M, Venketaraman V. Analysis of the delta variant B. 1.617. 2 COVID-19. Clin Pract. 2021; 11(4):778-84. [DOI:10.3390/clinpract11040093] [PMID] [PMCID]
40. Onishchenko GG, Sizikova TE, Lebedev VN, Borisevich SV. The omicron variant of the sars-cov-2 virus as the Dominant Agent of a New Risk of Disease amid the COVID-19 Pandemic. Her Russ Acad Sci. 2022; 92(4):381-91. [DOI:10.1134/S1019331622040074] [PMID] [PMCID]
41. Khare S, Gurry C, Freitas L, Schultz MB, Bach G, Diallo A, et al. GISAID›s role in pandemic response. China CDC Wkly. 2021; 3(49):1049-51. [DOI:10.46234/ccdcw2021.255] [PMID] [PMCID]
42. Gerdol M, Dishnica K, Giorgetti A. Emergence of a recurrent insertion in the N-terminal domain of the SARS-CoV-2 spike glycoprotein. Virus Res. 2022; 310:198674. [DOI:10.1016/j.virusres.2022.198674] [PMID] [PMCID]
43. Kumar S, Karuppanan K, Subramaniam G. Omicron (BA. 1) and Sub-Variants (BA. 1.1, BA. 2 and BA. 3) of SARS-CoV-2 Spike Infectivity and Pathogenicity: A Comparative Sequence and Structural-based Computational Assessment. 2022. [preprint].  [DOI:10.1101/2022.02.11.480029]
44. Clark C, Schrecker J, Hardison M, Taitel MS. Validation of reduced S-gene target performance and failure for rapid surveillance of sars-cov-2 variants. medRxiv. 2022. [DOI:10.1101/2022.04.18.22273989]
45. Wang Q, Guo Y, Iketani S, Nair MS, Li Z, Mohri H, et al. Antibody evasion by SARS-CoV-2 Omicron subvariants BA. 2.12. 1, BA. 4 and BA. 5. Nature. 2022; 608(7923):603-8. [DOI:10.1038/s41586-022-05053-w] [PMID] [PMCID]
46. Tegally H, Moir M, Everatt J, Giovanetti M, Scheepers C, Wilkinson E, et al. Emergence of SARS-CoV-2 omicron lineages BA. 4 and BA. 5 in South Africa. Nat Med. 2022; 28(9):1785-90. [DOI:10.1038/s41591-022-01911-2] [PMID] [PMCID]
47. Cao Y, Yisimayi A, Jian F, Song W, Xiao T, Wang L, et al. BA. 2.12. 1, BA. 4 and BA. 5 escape antibodies elicited by Omicron infection. Nature. 2022; 608(7923):593-602. [DOI:10.1038/s41586-022-04980-y] [PMID] [PMCID]
48. Ong CP, Ye ZW, Tang K, Liang R, Xie Y, Zhang H, et al. Comparative analysis of SARS-CoV-2 Omicron BA. 2.12. 1 and BA. 5.2 variants. J Med Virol. 2022; 95(1):e28326. [DOI:10.1002/jmv.28326]
49. Shaheen N, Mohamed A, Attalla A, Diab RA, Swed S, Nashwan AJ, et al. Could the New BA. 2.75 Sub-variant cause the emergence of a global epidemic of covid-19? A scoping review. Infect Drug Resist. 2022; 15:6317-30. [DOI:10.2147/IDR.S387551] [PMID] [PMCID]
50. Scarpa F, Sanna D, Benvenuto D, Borsetti A, Azzena I, Casu M,  et al. Genetic and structural data on the SARS-CoV-2 Omicron BQ. 1 variant reveal its low potential for epidemiological expansion. Int J Mol Sci. 2022; 23(23):15264. [DOI:10.3390/ijms232315264] [PMID] [PMCID]
51. Qu P, Evans JP, Faraone J, Zheng YM, Carlin C, Anghelina M, et al. Distinct neutralizing antibody escape of SARS-CoV-2 Omicron subvariants BQ. 1, BQ. 1.1, BA. 4.6, BF. 7 and BA. 2.75. 2. Biorxiv. 2022. [Preprint]. [DOI:10.1101/2022.10.19.512891]
52. Wang Q, Iketani S, Li Z, Liu L, Guo Y, Huang Y, et al. Alarming antibody evasion properties of rising SARS-CoV-2 BQ and XBB subvariants. Cell. 2022. [Preprint]. [DOI:10.1101/2022.11.23.517532]
53. Callaway E. Coronavirus variant XBB. 1.5 rises in the United States-is it a global threat? Nature. 2023; 613(7943):222-3. [DOI:10.1038/d41586-023-00014-3] [PMID]
54. Wang P, Nair MS, Liu L, Iketani S, Luo Y, Guo Y, et al. Antibody resistance of SARS-CoV-2 variants B. 1.351 and B. 1.1. 7. Nature. 2021; 593(7857):130-5. [DOI:10.1038/s41586-021-03398-2] [PMID]
55. Wibmer CK, Ayres F, Hermanus T, Madzivhandila M, Kgagudi P, Oosthuysen B, et al. SARS-CoV-2 501Y. V2 escapes neutralization by South African COVID-19 donor plasma. Nat Med. 2021; 27(4):622-5. [DOI:10.1038/s41591-021-01285-x] [PMID]
56. Wang P, Casner RG, Nair MS, Wang M, Yu J, Cerutti G, et al. Increased resistance of SARS-CoV-2 variant P. 1 to antibody neutralization. Cell Host Microbe. 2021; 29(5):747-51. e4. [DOI:10.1016/j.chom.2021.04.007] [PMID] [PMCID]
57. Planas D, Veyer D, Baidaliuk A, Staropoli I, Guivel-Benhassine F, Rajah MM, et al. Reduced sensitivity of SARS-CoV-2 variant Delta to antibody neutralization. Nature. 2021; 596(7871):276-80. [DOI:10.1038/s41586-021-03777-9] [PMID]
58. Khan K, Karim F, Ganga Y, Bernstein M, Jule Z, Reedoy K, et al. Omicron BA. 4/BA. 5 escape neutralizing immunity elicited by BA. 1 infection. Nat Commun. 2022; 13(1):4686. [DOI:10.1038/s41467-022-32396-9] [PMID] [PMCID]
59. Kaku CI, Starr TN, Zhou P, Dugan HL, Khalifé P, Song G, et al. Evolution of antibody immunity following Omicron BA. 1 breakthrough infection. bioRxiv. 2022. [preprint]. [DOI:10.1101/2022.09.21.508922]
60. Zeng B, Gao L, Zhou Q, Yu K, Sun F. Effectiveness of COVID-19 vaccines against SARS-CoV-2 variants of concern: A systematic review and meta-analysis. BMC Med. 2022; 20(1):200. [DOI:10.1186/s12916-022-02397-y] [PMID] [PMCID]
61. Zhang GF, Meng W, Chen L, Ding L, Feng J, Perez J, et al. Neutralizing antibodies to SARS-CoV-2 variants of concern including Delta and Omicron in subjects receiving mRNA-1273, BNT162b2, and Ad26. COV2. S vaccines. J Med Virol. 2022; 94(12):5678-90. [DOI:10.1002/jmv.28032] [PMID] [PMCID]
62. Rostami A, Sepidarkish M, Leeflang MMG, Riahi SM, Nourollahpour Shiadeh M, Esfandyari S, et al. SARS-CoV-2 seroprevalence worldwide: A systematic review and meta-analysis. Clin Microbiol Infect. 2021; 27(3):331-40. [DOI:10.1016/j.cmi.2020.10.020] [PMID] [PMCID]
63. Miller NL, Clark T, Raman R, Sasisekharan R. Insights on the mutational landscape of the SARS-CoV-2 Omicron variant receptor-binding domain. Cell Rep Med. 2022; 3(2):100527. [DOI:10.1016/j.xcrm.2022.100527] [PMID] [PMCID]
64. Almulla AF, Supasitthumrong T, Tunvirachaisakul C, Algon AAA, Al-Hakeim HK, Maes M. The tryptophan catabolite or kynurenine pathway in COVID-19 and critical COVID-19: A systematic review and meta-analysis. medRxiv. 2022. [preprint]. [DOI:10.21203/rs.3.rs-1408493/v1]
65. Walsh EE, Frenck Jr RW, Falsey AR, Kitchin N, Absalon J, Gurtman A, et al. Safety and immunogenicity of two RNA-based Covid-19 vaccine candidates. N Engl J Med. 2020; 383(25):2439-50. [DOI:10.1056/NEJMoa2027906] [PMID] [PMCID]