The World Health Organization, however, said that its confidence in the risk assessment of XBB.1.5 was low because growth advantage estimates are only from the U.S.
The highly transmissible omicron subvariant XBB.1.5 is threatening to drive a global increase in coronavirus cases, the World Health Organization said in a new rapid risk assessment of the strain.
“Based on its genetic characteristics and early growth rate estimates, XBB.1.5 may contribute to increases in case incidence globally,” the organization said in its assessment. But it noted that growth advantage estimates are only from the U.S., so it rated its confidence in the assessment as “low.”
WHO noted that there is no data available on XBB.1.5’s severity, but it said that it “does not carry any mutation known to be associated with potential change in severity.”
Similarly, there is no real-world data on how COVID-19 vaccines hold up against the strain, which is shown to be just as immune evasive as XBB.1, the omicron subvariant with the “highest immune escape to date,” WHO stated.
XBB.1.5’s spread in the U.S. is paired with increasing COVID-19 cases. The strain was responsible for nearly 28% of coronavirus cases last week. That’s up from 18% of cases the week before. It’s the only omicron subvariant showing growth in the U.S.
“It is the most transmissible subvariant that has been detected yet,” WHO’s Maria Van Kerkhove said about XBB.1.5 at a press briefing last week.
Notably, global COVID-19 cases and deaths decreased last week, according to WHO’s weekly COVID-19 report. But WHO Director-General Tedros Adhanom Ghebreyesus said at a press briefing on Wednesday that last week’s death toll is “almost certainly an underestimate given the under-reporting of COVID-related deaths in China.”
China is in the midst of a COVID-19 surge, but WHO and others have had trouble getting adequate data out of the country to assess the full extent of the wave.
The U.N. agency “still believes that deaths are heavily underreported from China,” WHO’s Mike Ryan said at Wednesday’s press conference.
“We still do not have adequate information to make a full comprehensive risk assessment and, therefore, we will continue to try to encourage access to that data,” Ryan said, adding that some progress has been made.