(GIST OF SCIENCE REPORTER) Variants
- Viruses mutate and evolve with time and conditions. The genetic markers of the virus change and thus their receptor binding, reduced neutralisation by antibodies, efficacy of treatments, potential diagnostic impact, transmissibility and/or disease severity also changes. The changed viral entities are called variants of the viruses.
Variant of Interest (VoI)
- According to the Center for Disease Control and Prevention-USA, a variant of interest may have the following attributes:
- Specific genetic markers that can affect transmission rates, diagnostics, therapeutics or immune escape.
- Evidence that they are the cause of an increased proportion of cased or unique outbreak clusters.
- Limiting prevalence or expansion.
Variant of Concern (VoC):
A variant is identified as a ‘variant of concern’ if there are clear evidences of an increase in transmissibility and severity of disease, significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatment or vaccines, or diagnostic detection failures caused by the virus variant. According to the Center for Disease Control and Prevention-USA, the possible attributes of a variant of concern are (in addition to the possible attributes of a variant of interest):
- 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 significant decreased neutralisation 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 mutant virus is identified as a variant of high consequence if there are clear evidences that the prevention measures or the medical counter measures have significantly reduced effectiveness relative to the previously circulating variants.
- According to the Center for Disease Control and Prevention-USA, the possible attributes of a variant of high consequence are (in addition to the possible attributes of a variant of concern):
Impact on Medical Countermeasures (MCM):
- Demonstrated failure of diagnostics
- Evidence to suggest a significant reduction in vaccine effectiveness, a disproportionately high number of vaccine breakthrough cases, or very low vaccine induced protection against severe disease.
- Significantly reduced susceptibility to multiple Emergency Use Authorisation (EUA) or approved therapeutics
- More severe clinical disease and increased hospitalisations
- The World Health Organization issues a notification under the International Health Regulations regarding the variant of high consequence. WHO also releases notifications related to strategies for prevention and containment of the variant, including its treatment and vaccines. Till now, WHO has not identified any variant as a variant of high consequence.
Courtesy: Science Reporter