XBB.1.5 is a sub-Omicron variant. It becomes dominant Covid-19 and spread rapidly in the US and around the World. Early indication shows that the new variant is not deadly compared to other variants. Some epidemiologists believe that the immune systems take longer to recognize the new variant. It means our bodies take longer to produce antibodies to neutralize the new variant. As we know that how people get sick depends on how much virus is in the body. As a result, people are more chances to develop Covid symptoms.
We should not worry about the new variant because the vaccine still gives some protection against Covid diseases. The vaccinated people are less likely to develop severe or dead. A booster shot may be advised for some people.
The variant is born when the virus mutates during its multiplication.