What is XBB.1.5?
XBB.1.5 is yet another omicron subvariant, and follows on from XBB and XBB.1. Scientists have nicknamed it “kraken” to distinguish it from the “variant soup” we are all navigating three years into the pandemic.

According to UCL Genetics Institute director Francois Balloux, a professor of computational systems biology, XBB.1.5 differs from XBB.1 through the addition of a F486P mutation in the spike protein. “This mutation makes it slightly less immune evasive than its XBB.1 ancestor but more infectious, probably because it increases binding affinity to the human cell receptor ACE-2,” he said.

Where is XBB.1.5 spreading?
The World Health Organization has reported that XBB.1.5 is present in 38 countries.3

The UK Health Security Agency (UKHSA) said it is one of two variants most likely to become dominant in the UK, despite representing less than 5% of all SARS-CoV-2 samples sequenced in the last week of 2022. The agency has described the variant as having a combination of “immune escape properties” and a higher ACE-2 binding affinity, which it said could lead to higher transmissibility.

Meanwhile, the European Centre for Disease Prevention and Control (ECDC) has said there is a “moderate probability” that XBB.1.5 will become dominant across the European Union and European Economic Area and cause a “substantial increase in the number of covid-19 cases within the next one to two months.”

In the US the Centers for Disease Control and Prevention has said the variant is “spreading quickly” and is estimated to make up around 28% of cases in the country (week ending 7 January 2023).

Does it cause more severe illness?
This is still under review. According to WHO, however, XBB.1.5 “does not carry any mutation known to be associated with potential change in severity.”

Do the current covid vaccines protect against XBB.1.5?
Specific vaccine effectiveness estimates are not yet available for XBB.1.5, but WHO has warned that it may have the “highest immune escape to date.” Its evidence suggests people who have had three or four doses of an mRNA covid-19 vaccine (such as Moderna or Pfizer) plus.
Source -Bmj