What do we know about COVID-19 OMICRON Variant?
With the emergence of Omicron variant, uncertainty seems only certain at this point of time. However, with the proactive approach of searcher and scientists across the globe and World Health Organisation (WHO), some sort of conclusion is appearing. On 26 November 2021, WHO designated the variant B.1.1.529 a variant of concern (VOC).
The variant has been named Omicron. Among the Omicron variants, there are 26-32 mutations in the spike protein, some of which are concerning and may be linked with immune evasion ability and higher transmissibility. Human infections with this variant have been reported in 63 countries across all six WHO regions as of 9 December 2021.
World Health Organisation (WHO) considers that threat posed by Omicron largely depends on three key questions, including: (1) how transmissible the variant is; (2) how well vaccines and prior infection protect against infection, transmission, clinical disease and death; and (3) how virulent the variant is compared to other variants.
On 5th December, Ministry of Health, Singapore shared information related to vaccine efficacy and transmissibility.
How transmissible is OMICRON Variant?
WHO observes that Omicron seems to be growing faster than Delta. In South Africa where Delta circulation was low, it spreads faster than the Delta variant, but it also seems to spread faster in other countries with high Delta incidence, like the UK. Whether Omicron’s observed rapid growth rate in countries with high levels of population immunity is related to immune evasion, intrinsic increased transmissibility, or a combination of both remains uncertain. However, based on the data we have right now, Omicron is more likely to outpace the Delta variant.
On 5th December, Ministry of Health, Singapore reported the variant may have increased transmissibility.
Are vaccines effective against OMICRON Variant?
To date, there are no peer-reviewed studies on Omicron’s efficacy or effectiveness. Based on preliminary evidence and the dramatically altered antigenic profile of Omicron spike protein, there may be a reduction in vaccine effectiveness against infection and transmission of Omicron. There is some preliminary evidence that reinfections are increasing in South Africa, and it may be due to humoral (antibody-mediated) immune evasion. In addition, preliminary evidence from a few studies of limited sample size has shown that sera obtained from vaccinated and previously infected individuals had lower neutralization activity (the size of the reduction ranges considerably) than with any other circulating VOCs of SARS-CoV-2 and the ancestral strain.
Are existing testing methodologies detecting OMICRON Variant?
Omicron doesn’t seem to affect the diagnostic accuracy of routine PCR and antigen-based rapid diagnostic tests (Ag-RDTs). Most Omicron variant sequences reported include a deletion in the S gene, causing some S gene targeting PCR assays to appear negative. Although some publicly shared sequences lack this deletion, this remains a minority of currently available sequences, and S gene target failure (SGTF) can therefore be used as a useful proxy marker of Omicron, for surveillance purposes. However, confirmation should be obtained by sequencing, as this deletion can also be found in other VOCs (e.g., Alpha and subsets of Gamma and Delta.