New omicron subvariant surges to 40.5% as COVID hospitalizations rise

A new omicron coronaviruses subvariant dubbed XBB. 1.5 now accounts for an estimated 40.5 percent of all US COVID-19 cases amid a winter wave that is driving up hospitalizations.

New reported cases are around 59,000 per day, which is still low compared with previous waves. The case data has become murkier over the 3-year-old Pandemic with fewer testing sites available and the results of common at- home tests not being reported. Case reports may jump in the coming days as backlogged data rolls in due to the lag in data reporting.

According to data tracked by The New York Times, hospitalizations are on the rise. The national hospitalization rates are close to those from the peak over the summer. The areas with the largest increases in hospitalizations are those where the new subvariant XBB. 1.5 is most common. In the Northeast, XBB. 1.5 has the highest regional proportion, accounting for 75 percent of cases, and hospitalizations have risen 16 percent over the prior seven days, the largest region-specific rise.

Wave factors

XBB. 1.5 is not causing more severe disease than previous versions. There are a number of reasons why hospitalizations may be increasing. Older adults who are most vulnerable to severe disease are less likely to take the bivalent booster. Only 15 percent of Americans aged 5 and over have gotten their bivalent shot, and only 35 percent of people over the age of 65 have been boosted. In December, the CDC quietly expanded access to the vaccine for children aged 6 months to 5 years, but just 3 percent of the population has completed the series.

With holidays and cold weather, people are spending more time indoors. There have been increases in hospitalizations in places where XBB. 1.5 hasn't taken off. In the South, XBB. 1.5 only accounts for 19 percent of cases, with BQ. 1.1 accounting for 41.5%. Over the past week, hospitalizations in the region have increased.

XBB. 1.5 has a clear transmission advantage and is expected to spread throughout the country. The sublineage of omicron XBB is a combination of two separate sublineages. The original XBB has three significant changes compared to XBB.

Data published last month in the New England Journal of Medicine offered some good news regarding vaccine protection, despite early research suggesting that XBB. 1.5 is more immune-evasive than its predecessors. The data indicated that people boosted with the BA.5-targeting bivalent vaccine used in the US had stronger neutralizing antibodies against XBB than those who had only received the original booster.