Table 1.
Comparison of the characteristics of pandemic SARS-CoV-2 variants.
| WHO Label | Alpha | Delta | Omicron |
|---|---|---|---|
| Pango Lineage | B.1.1.7, Q | B.1.617.2, AY.4.2 | B.1.1.529, BA |
| First detected | United Kingdom | India | South Africa |
| September 2020 | December 2020 | November 2021 | |
| Key amino acid substitutions in spike protein | N501Y, D614G, and P681H | L452R, T478K, D614G, and P681R | 30 changes, 3 small deletions, and 1 small insertion * |
| Infectivity Transmissibility | ↑ | ↑~↑↑ | ↑↑↑ |
| 43–82% more transmissible than the ancestral lineage | At least equal to alpha | RtOmicron 3.19–4.2 times greater than RtDelta, with higher secondary attack rates | |
| Clinical severity | →/↑ | ↑↑ | ↓ |
| 60% higher mortality than the ancestral lineage | risk for hospital admission twice as high as alpha | Decrease in severity and mortality | |
| Immune escape | → | ↑ | ↑↑ |
| Higher reinfection rate and reduced vaccine efficacy | |||
| Diabetogenecity | Insufficient data ** | No data | No data |
* A67V, del69-70, T95I, del142-144, Y145D, del211, L212I, ins214EPE, G339D, S371L, S373P, S375F, K417N, N440K, G446S, S477N, T478K, E484A, Q493R, G496S, Q498R, N501Y, Y505H, T547K, D614G, H655Y, N679K, P681H, N764K, D796Y, N856K, Q954H, N969K, and L981F (RBD substitutions in bold type). ↑: increased; ↓: decreased; Rt: effective reproduction number. ** A study supporting new-onset diabetes [70] included data during the period when the alpha variant was dominant. References: [91], transmissibility [92,93,94], Rt [95,96], secondary infection rate [97], severity [86,92,98,99], reinfection [100], and immune escape [89].