What Is the New Covid Variant XBB.1.5? What Do We Know About It?

A new subvariant of SARS-CoV-2, the coronavirus causing Covid-19, XBB.1.5, has increasingly spread and become a concern. It descends from the Omicron variant and has begun to spread widely around the world.

For Covid-19 caused by XBB.1.5, the symptoms are expected to resemble those of previous Omicron variants, although it is too early to be certain. Most people experience cold-like symptoms.

Is XBB.1.5 More Transmissible or Dangerous than Earlier Variants?

XBB.1.5 descends from XBB, which began spreading in the UK in September 2022 and was not classified by health authorities as a variant of concern; it arose from the XBB variant.

XBB had a mutation allowing it to evade the body’s immune system, a mutation that also reduced the virus's ability to infect human cells.

Scientists reported that XBB.1.5 has a new mutation called F486P, restoring its ability to bind to cells while retaining immune evasion. It therefore spreads more easily. These evolutionary changes are like “necessary steps” for a virus seeking to evade the body's own defences.

World Health Organization (WHO) scientists confirmed that XBB.1.5 has a greater growth advantage than other subvariants seen so far. However, they stated that there was no indication that it was more severe or harmful than previous Omicron variants. WHO said it would closely monitor laboratory studies, hospital data and infection rates to learn how the variant affects patients.

Where Is It Spreading?

XBB.1.5 has become responsible for 40 percent of Covid cases in the US, rapidly overtaking other Omicron variants as the leading variant. XBB.1.5 has also begun accounting for 25 percent of UK Covid cases and may become more common in a few weeks. We do not yet have clear data on the prevalence of XBB.1.5 in our country.

More hospital admissions are expected if XBB.1.5 spreads. Covid vaccination also provides an advantage against XBB.1.5. However, it may affect vulnerable groups with weaker immune systems who benefit less from vaccination.

XBB.1.5 cannot be said to cause milder disease than Omicron, while it is stated that it will not cause more hospitalisations and deaths than existing Omicron variants.

China or the United States?

Although XBB.1.5 might have emerged in China, it is thought to have originated in the US. While much remains to be learned about XBB.1.5, it is not expected to create major problems in countries with high vaccination rates. The main concern is countries with low effective vaccination coverage and low natural immunity due to prolonged lockdowns, particularly China. It is therefore essential for China to share actual clinical information about infected people.