The Delta and Omicron Variants of SARS-CoV-2: What We Know So Far

Abstract

The world has not yet completely overcome the fear of the havoc brought by SARS-CoV-2. The virus has undergone several mutations since its initial appearance in China in December 2019. Several variations (i.e., B.1.616.1 (Kappa variant), B.1.617.2 (Delta variant), B.1.617.3, and BA.2.75 (Omicron variant)) have emerged throughout the pandemic, altering the virus’s capacity to spread, risk profile, and even symptoms. Humanity faces a serious threat as long as the virus keeps adapting and changing its fundamental function to evade the immune system. The Delta variant has two escape alterations, E484Q and L452R, as well as other mutations; the most notable of these is P681R, which is expected to boost infectivity, whereas the Omicron has about 60 mutations with certain deletions and insertions. The Delta variant is 40–60% more contagious in comparison to the Alpha variant. Additionally, the AY.1 lineage, also known as the “Delta plus” variant, surfaced as a result of a mutation in the Delta variant, which was one of the causes of the life-threatening second wave of coronavirus disease 2019 (COVID-19). Nevertheless, the recent Omicron variants represent a reminder that the COVID-19 epidemic is far from ending. The wave has sparked a fervor of investigation on why the variant initially appeared to propagate so much more rapidly than the other three variants of concerns (VOCs), whether it is more threatening in those other ways, and how its type of mutations, which induce minor changes in its proteins, can wreck trouble. This review sheds light on the pathogenicity, mutations, treatments, and impact on the vaccine efficacy of the Delta and Omicron variants of SARS-CoV-2.

Targeting SARS-CoV-2 and host cell receptor interactions

“…As of November 2022, over 30 Abs are listed as having completed or still undergoing clinical trials ( Antibodysociety.org , accessed November 2022). Nevertheless, due to the dynamic antigenic shifts in SARS-COV-2 strains and subvariants, and the dominance of the Omicron strain from November 2021 ( Chavda et al, 2022 ), some setbacks have been encountered. Most trials are designed to check antibody efficacy in patients with mild or moderate COVID-19 and at high risk of disease progression or hospitalisation, with a few early trials designed to assess mAbs efficacy in hospitalised COVID-19 patients.…”

Omicron Variant of SARS-CoV-2: An Indian Perspective of Vaccination and Management

“…Later, a new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant with an amino acid mutation in the spike protein was reported to increase the severity of the disease [ 1 , 2 ]. The World Health Organization (WHO) divides variants into different categories, such as variants of concern (VOCs), variants of interest (VOIs), and variants under monitoring (VUMs) [ 3 , 4 ]. VOCs incorporate alpha, beta, gamma, and delta variants of SARS-CoV-2 [ 5 ].…”

“…The delta (B.1.617.2) variant was first recognized in India as a VOC in October 2020. It is more contagious than previous alpha and beta previous variants [ 4 , 7 ]. Mutations in its receptor binding domain, namely, T478K and L452R, increase the transmission rate and infectivity rate of the delta variant [ 8 ].…”

COVID-19-Related Burnout and Intention of Fully Vaccinated Individuals to Get a Booster Dose: The Mediating Role of Resilience

“…However, the vaccination rate in low-income countries is very low as only 23.6% of citizens in these countries have received at least one dose of a COVID-19 vaccine [ 1 ]. Moreover, the effectiveness of primary vaccination (a) against severe disease decreases within six months [ 5 , 6 ] and (b) against new variants (e.g., the Delta and Omicron variants) is limited [ 7 , 8 ]. Therefore, several countries have already approved booster doses, especially in high-risk groups.…”