COVID-19. Omicron Variant
On November 24, 2021, South Africa reported the identification of a new SARS-CoV-2 variant, B.1.1.529, to the World Health Organization (WHO). B.1.1.529 was first detected in specimens collected on November 11, 2021, in Botswana and on November 14, 2021, in South Africa. On December 1, 2021, the first case attributed to B.1.1.529 was reported in the United States in a person who returned from travel to South Africa. The Omicron variant has also been detected in travel-related cases in several European countries, as well as Australia, Brazil, Canada, Hong Kong, Israel, Japan, Nigeria, Norway, Sweden, and the United Kingdom. A few countries, including Greece, have reported cases in individuals without travel history to southern Africa.
The WHO classification as a «Variant of Concern» (VOC) was based on epidemiological data indicating an increase in infections in South Africa in recent weeks that coincided with the detection of Omicron. Omicron has many concerning spike protein substitutions, some of which are known from other variants to be associated with reduced susceptibility to available monoclonal antibody therapeutics or reduced neutralization by convalescent and vaccinee sera. The European Center for Disease Prevention and Control also classified this variant as a VOC due to concerns «regarding immune escape and potentially increased transmissibility compared to the Delta variant».
There are two variants classified as a VOC: Omicron and Delta. Delta continues to be the predominant circulating variant. Importantly, nearly all lineages designated as Delta remain susceptible to available monoclonal antibody therapeutics, and vaccines continue to be highly effective against severe illness, hospitalization, and death among people infected with the Delta variant.
Omicron (B.1.1.529) Characteristics
Transmissibility: Currently, it is unknown how efficiently the Omicron variant can spread from person to person. The replacement of Delta by Omicron as the predominant variant in South Africa raises concerns that the Omicron variant may be more transmissible than Delta, but due to the low number of cases in South Africa when Omicron emerged, it is unclear if this variant is more transmissible than the Delta variant. Further, the relatively small number of cases documented to date makes it difficult to estimate transmissibility. Analysis of the changes in the spike protein indicates that the Omicron variant is likely to have increased transmission compared to the original SARS-CoV-2 virus, but it is difficult to infer if it is more transmissible than Delta.
Disease Severity: Currently, it is unclear if infection with the Omicron variant is associated with a more severe disease. Due to the small number of cases attributed to the Omicron variant, assessment of disease severity is difficult. Preliminary information from South Africa indicates that there are no unusual symptoms associated with Omicron variant infection, and as with other variants, some patients are asymptomatic.
Impact on Vaccine-Induced Immunity or Immunity from Previous Infection: Currently, there are no data available to assess the ability of sera from vaccinated persons or those with previous SARS-CoV-2 infection to neutralize the Omicron variant.
The spike protein (S) is the primary target of vaccine-induced immunity. The Omicron variant contains more changes in the spike protein than have been observed in other variants, including 15 in the Receptor Binding Domain (RBD). Based on the number of substitutions, the location of these substitutions, and data from other variants with similar spike protein substitutions, significant reductions in neutralizing activity of sera from vaccinated or previously infected individuals, which may indicate reduced protection from infection, are anticipated.
Impact on Monoclonal Antibody Treatments: Currently, there are no virus-specific data available to assess whether monoclonal antibody treatments will retain efficacy against the Omicron variant. Based on data from other variants with significantly fewer changes in the RBD, the expectation is that the Omicron variant will remain susceptible to some monoclonal antibody treatments, while others may have less potency.
At Diagnostiki Athinon we perform a molecular test for coronavirus (PCR test) with the ability to separate the Omicron and Delta variants. Coronavirus COVID-19, Omicron & Delta Variants