COVID-19 mutations: An overview

Table 1 Showing characteristic features of various variants of concerns

VOCs	Transmissibility	Severity	Effect on neutralization by mABs		SGTF	Present status	Vaccine efficacy
Alpha	Increased transmissibility (50%-100%) with R0 1.75-fold higher compared to original lineage[32]	Increased severity. Hazard of death of 55% (95%CI: 39%–72%) higher than in cases without SGTF after adjustment[33]	No impact on neutralization by mABs, and minimal impact by convalescent and/or post-vaccination sera[18]. E484K and/or various NTD mutations cause a significant fall in neutralization efficacy[39]		Presence	De-escalated	The ChAdOx1 nCoV-19 vaccine showed an efficacy of 70.4%[40]. The first and second dose of BNT162b2 vaccine (Pfizer–BioNTech) reported 48.7% and 93.7% effectiveness, respectively[41]. The reported efficacy of 2-doses of mRNA-1273 vaccine 98.4%[42]
Beta	Increased transmissibility	Increased risk of hospitalization, ICU admission, and mortality in comparison to Alpha and Gamma variants, but less severe disease compared to Delta[44]	45-fold decreased susceptibility to Bamlanivimab-etesevimab therapy. Casirivimab-imdevimab and sotrovimab retained susceptibility[38-40]. Moderate reduction in neutralization by convalescent and post-vaccination sera[45]		Absent	De-escalated	Full vaccination efficacy 73.0% (95%CI: 64.3%–79.5%)[46]
Gamma	1.7 to 2.4-fold higher transmissible than previous (non-P.1) infection[48]. Increased risk of reinfection	1.2 to 1.9 times more likely to result in mortality compared with previous lineages[48]	> 511 fold decreased susceptibility to Bamlanivimab-etesevimab but no change in susceptibility with Casirivimab-imdevimab and Sotrovimab[38-40]. Reduced neutralization to convalescent and post-vaccination sera		Absent	De-escalated	Full vaccination efficacy against Gamma variants 63.0% (95%CI: 47.9%–73.7%)[46]
Delta	40%-60% more transmissible than Alpha variant[49]	Increased severity of the disease[51,52] and increased risk of hospitalization[52,53].A shorter time interval between disease onset to hospitalization in comparison to the wild-type variant[44]	Neutralization is affected minimally		Absent	De-escalated	Moderate reduction in vaccine efficacy against symptomatic infection but retained efficacy against severe disease and hospitalization[45]. The 2-dose mRNA-1273 vaccine: 86.7% (95%CI: 84.3%-88.7%) efficacy against infection and 97.5% (92.7%-99.2%) efficacy against hospital admission. The 2-doses of BNT162b2 and ChAdOx1 nCoV-19 vaccine 88.0% (95%CI: 85.3%-90.1%) and 67.0% (95%CI: 61.3%-71.8%), respectively[41]
Omicron	Increased risk of transmissibility, reinfection/breakthrough infection	Severity less compared to Delta variant	Reduced or absent neutralization efficacy by vaccines and mABs[56]		SGTF except BA.2 lineage[64]	Few sublineages de-escalated (BA.1, BA.2, BA.3, BA.4, BA.5 etc.)	Booster doses are needed to mount a more appropriate immune response against symptomatic or non-symptomatic infections, transmission, and serious manifestations[44]

VOCs: Variants of concerns; SGTF: “S” gene target failure; ICU: Intensive care unit; mAbs: Monoclonal antibodies; NTD: N-terminal domain.