Will BA.4, BA.5 Omicron lineages cause the next wave?
- May 8, 2022
- Posted by: OptimizeIAS Team
- Category: DPN Topics
Will BA.4, BA.5 Omicron lineages cause the next wave?
Subject: Science
Section: Disease
Context: A group of variants with similar genetic changes or group of lineages’
Concept: World Health Organization (WHO) designated the B.1.1.529 lineage of SARS-CoV-2 as Variant of Concern (VOC) Omicron in late Nov 2021. Omicron is more transmissible (e.g., more easily spread from person to person) and has the ability to infect people who had prior immunity to Delta or any previous lineages of the virus.
Lineage: A lineage is a group of closely related viruses with a common ancestor. SARS-CoV-2 has many lineages; all cause COVID-19.
Variant: A variant is a viral genome (genetic code) that may contain one or more mutations. In some cases, a group of variants with similar genetic changes, such as a lineage or group of lineages, may be designated by public health organizations as a Variant Being Monitored (VBM), Variant of Concern (VOC) or a Variant of Interest (VOI) due to shared attributes and characteristics that may require public health action.
What does it mean a virus mutates or changes?
When a virus replicates or makes copies of itself, it sometimes changes a little bit. These changes are called “mutations.” A virus with one or several new mutations is referred to as a “variant” of the original virus. When more viruses circulate, the more they may change. These changes can occasionally result in a virus variant that is better adapted to its environment compared to the original virus. This process of changing and selecting successful variants are called “virus evolution.”
Some mutations can lead to changes in a virus’s characteristics, such as altered transmission (for example, it may spread more easily) or severity (for example, it may cause a more severe disease).
Some viruses change quickly and others more slowly. SARS-CoV-2, the virus which causes COVID-19, tends to change more slowly than others such as HIV or influenza viruses. This could in part be explained by the virus’s internal “proofreading mechanism” which can correct “mistakes” when it makes copies of itself. Scientists continue to study this mechanism to better understand how it works.
Concerning facts of SARS-CoV-2 changing
It is normal for viruses to change, but it is still something scientists follow closely because there can be important implications.
All viruses, including SARS-CoV-2, the virus that causes COVID-19, change over time. So far hundreds of variations of this virus have been identified worldwide.
Most changes have little to no impact on the virus’ properties. However, depending on where the changes are located in the virus’s genetic material, they may affect the virus’s properties, such as transmission (for example, it may spread more easily) or severity (for example, it may cause more severe disease).
Genetic lineages of SARS-CoV-2 have been emerging and circulating around the world since the beginning of the COVID-19 pandemic.
SARS-CoV-2 genetic lineages are routinely monitored through epidemiological investigations, virus genetic sequence-based surveillance, and laboratory studies.
The classification of SARS-CoV-2 genetic lineages was based on the following:
- Detection of cases attributed to Omicron in multiple countries, including among those without travel history.
- Transmission and replacement of the Delta variant in South Africa.
- The number and locations of substitutions in the spike protein.
- Available data for other variants with fewer substitutions in the spike protein that indicate a reduction in neutralization by sera from vaccinated or convalescent individuals.
- Available data for other variants with fewer substitutions in the spike protein that indicate reduced susceptibility to certain monoclonal antibody treatments.
- On April 14, 2022 SARS-CoV-2 Interagency Group (SIG) downgraded Delta from a Variant of Concern to a Variant Being Monitored. This new classification was based on the following:
- Significant and sustained reduction in its national and regional proportions over time.
- Evidence suggesting that Delta does not currently pose a significant risk to public health in the United States.
- The SIG Variant classification scheme defines four classes of SARS-CoV-2 variants:
o Variant Being Monitored (VBM)
- Alpha (B.1.1.7 and Q lineages)
- Beta (B.1.351 and descendent lineages)
- Gamma (P.1 and descendent lineages)
Delta (B.1.617.2 and AY lineages)
- Epsilon (B.1.427 and B.1.429)
- Eta (B.1.525)
- Iota (B.1.526)
- Kappa (B.1.617.1)
- 617.3
- Mu (B.1.621, B.1.621.1)
- Zeta (P.2)
o Variant of Interest (VOI)
o Variant of Concern (VOC)
- Omicron (B.1.1.529, BA.1, BA.1.1, BA.2, BA.3, BA.4 and BA.5 lineages)
o Variant of High Consequence (VOHC)
How Variants Are Classified
With the continuous evolution of SARS-CoV-2 and understanding of the impact of variants on public health, variants may be reclassified based on their attributes and prevalence.
- Variants being monitored (VBM)–
- Variant of interest (VOI)
- Variant of Concern (VOC)
- Variant of high consequence (VOHC)
Variants Being Monitored (VBM): Variants designated as VBM include those where data indicates there is a potential or clear impact on approved or authorized medical countermeasures or that has been associated with more severe disease or increased transmission but are no longer detected, or are circulating at very low levels.
Variant of Interest (VOI)
A variant with specific genetic markers that have been associated with changes to receptor binding, reduced neutralization by antibodies generated against previous infection or vaccination, reduced efficacy of treatments, potential diagnostic impact, or predicted increase in transmissibility or disease severity.
Possible attributes of a Variant of Interest:
- Specific genetic markers that are predicted to affect the transmission, diagnostics, therapeutics, or immune escape.
- Evidence that it is the cause of an increased proportion of cases or unique outbreak clusters.
- Limited prevalence or expansion in the US or in other countries.
Variant of Concern (VOC)
A variant for which there is evidence of an increase in transmissibility, more severe disease (for example, increased hospitalizations or deaths), a significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatments or vaccines, or diagnostic detection failures.
Possible attributes of a variant of concern:
- Evidence of impact on diagnostics, treatments, or vaccines
- Widespread interference with diagnostic test targets
- Evidence of substantially decreased susceptibility to one or more class of therapies
- Evidence of significantly decreased neutralization by antibodies generated during previous infection or vaccination
- Evidence of reduced vaccine-induced protection from severe disease
- Evidence of increased transmissibility
- Evidence of increased disease severity
Variant of High Consequence (VOHC): A VOHC has clear evidence that prevention measures or medical countermeasures (MCMs) have significantly reduced effectiveness relative to previously circulating variants.
Possible attributes of a variant of high consequence:
- Impact on MCMs
- Demonstrated failure of diagnostic test targets
- Evidence to suggest a significant reduction in vaccine effectiveness, a disproportionately high number of infections in vaccinated persons, or very low vaccine-induced protection against severe disease
- Significantly reduced susceptibility to multiple EUA or approved therapeutics
- More severe clinical disease and increased hospitalizations