The World Health Organization (WHO) Technical Advisory Group on Virus Evolution (TAG-VE) on June 25 added the XFG to its SARS-CoV-2 variants under monitoring (VUM) list, as global proportions increase rapidly. In its initial risk assessment, the experts said the public health risk is currently low.

XFG is one of many offshoots of the JN.1 subvariant, and the earliest sample was collected at the end of January. It is a recombinant of LF.7 and LP.8.1.2. Compared to NB.1.8.1, designated as a VUM at the end of May, XFG has some distinct mutations in the spike protein, but also some overlap. Two of the spike mutations are linked to evasion of class 1/2 antibodies.
Experiments with pseudoviruses show a 1.9-fold reduction in neutralization compared to LP.8.1.1. Studies involving vaccinated mice showed similar or modestly lower neutralizing antibodies against XFG compared to KP.2 or LP.8.1 antigens.
Proportions highest in Southeast Asia
In May, the proportion of XFG viruses rose in all three WHO regions that consistently share SARS-CoV-2 sequences, especially in Southeast Asia. Cases and hospitalizations are rising in countries where XFG proportions are high, but so far there is no sign that infections are more severe.
In the United States, XFG made up 14% of sequenced samples, according to the latest variant proportion update from the Centers for Disease Control and Prevention (CDC) on data through June 21.
Overall, the WHO team said XFG seems to have a moderate growth advantage and a low risk of immune escape, though confidence in the assessments are low, owing to recent expansion and low levels of sequencing. Also, only one study has been done to assess antigenicity.