New strain could evade vaccines, CDC warns

As Omicron variants of the coronavirus continue to evolve, the XBB.1.5 strain appears to evade vaccines and past infections and has grown at a fast pace in the United States, doubling its infection numbers every week for the last four weeks, the Centers for Disease Control and Prevention said.

CDC data showed that between Dec 25 and 31, XBB.1.5 accounted for more than 40 percent of all new COVID-19 cases. It has been spreading especially fast in the Northeast, where the variant accounted for about 75 percent of all new infections.

CNN reported that David Ho, a professor of microbiology and immunology at Columbia University, found that XBB.1 was the most slippery of all subvariants in his lab. It was 63 times less likely to be neutralized by antibodies in the blood of infected and vaccinated people than BA.2, and 49 times less likely to be neutralized compared with BA.4 and BA.5.

That means XBB.1.5 can easily evade antibodies from prior infection, vaccines and existing monoclonal antibody treatments.

Ho said these levels of immune evasion are "alarming" and they could further compromise the efficacy of COVID-19 vaccines.

In addition, XBB.1.5 has proved to be highly contagious. The new variant has a key mutation that allows it to bind more tightly to ACE2, the hooks the virus uses to enter cells.

Virologists and public health researchers are concerned that the new Omicron sublineage could potentially drive a new surge of coronavirus cases in the US.

However, some experts said it is hard to know how much of XBB.1.5's growth can be attributed to properties of the virus and to the holiday timing when people are more likely to travel and gather, thus giving the virus more chances to infect people.

Some are optimistic when looking at the situation in the US Northeast.

Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told CNN that updated boosters should provide some protection.

"They still provide a level of immunity that may not prevent you from getting infected, but may have a significant impact on whether or not you become seriously ill and die," he said.

Jay Varma, public health researcher and director of the Cornell Center for Pandemic Prevention and Response, told PBS that while the XBB.1.5 is going to cause some ups and downs, "it doesn't appear that it's going to increase their risk of hospitalization and death beyond what has already happened in the past before".