Covid: the variant called Kraken is now the dominant one, in the USA as in the United Kingdom and soon probably throughout Europe. More immunoevasive and transmissible, but no more serious. The evidence on the variant of Sars-CoV-2 Omicron XBB.1.5, renamed Kraken, is strengthened from the latest report released by the WHO.
Kraken more transmissible, not more serious
“There is evidence of an increased risk of transmission and immune escape. This evidence is of moderate strength.” Based on its genetic characteristics and growth rate estimates, it “is likely to contribute to the increased incidence of ‘Covid’ cases globally.” From reports from several countries, “no early signs of increased severity have been observed.” But, it is pointed out, “the number of cases associated with XBB.1.5 is still low and therefore the severity cannot yet be assessed with confidence”.
Taken together, the WHO assessment concludes, the available information suggests that Kraken “does not appear to have any additional public health risks compared to other Omicron descendant lineages.” The new analysis ofUN health agency It comes after the latest expert meeting of the WHO Technical Advisory Group on Virus Evolution (TAG-Ve), which was held on 23 January. WHO has also revised the level of confidence in the risk assessment, which now rises from low (January 11) to moderate (January 25), as the analysis relied on additional reports from countries on the prevalence and benefit of Kraken growth and additional laboratory studies.
increasingly dominant variant
XBB.1.5 is the descendant lineage of XBB, recombinant of two BA.2 descendant lineages. Most of his sequences deposited in the database come from the USA. From October 2022 to January 23, 2023, 8,931 Kraken sequences were reported from 54 countries, 75% of which were from the United States. The countries with a prevalence above 1% are the United Kingdom (9.9%), Canada (3%), Denmark (2%), Germany (1.5%), Ireland (1.3%) and Austria (1.3%).
Monitoring
WHO and TAG-Ve recommend Member States prioritize studies to overcome the uncertainties related to growth advantage, antibody escape and severity of XBB.1.5. Overall the agency is currently closely monitoring four Omicron descendant lineages: BF.7, the BQ.1 group (and BQ.1.1 Cerberus), BA.2.75 Centaurus (including its ‘children’ BA.2.75.2 and CH.1.1) and the XBB family (including Kraken XBB.1.5). The risk analysis is disseminated precisely for the latter.
