The BA.2 virus-- a subvariant of the Omicron coronavirus variant-- isn't just spreading faster than its distant cousin, it may also cause more severe disease and appears capable of thwarting some of the key weapons we have against Covid-19, new research suggests. New lab experiments from Japan show that BA.2 may have features that make it as capable of causing serious illness as older variants of Covid-19, including Delta. And like Omicron, it appears to largely escape the immunity created by vaccines. A booster shot restores protection, making illness after infection about 74% less likely. BA.2 is also resistant to...