On Wall Street, the end of the pandemic appeared tantalizingly close just a week ago. There were positive signs the economy was rebounding, and investors’ biggest worry was how quickly the Federal Reserve would pivot away from the market-boosting policies that have helped stocks soar in the past year and a half.The Omicron variant changed that almost overnight.Investors and analysts have snapped their attention back on the virus as they try to assess the myriad ways the concerning new iteration could undermine an often overlooked source of market confidence this year: the effectiveness of vaccines.Now the markets face weeks of uncertainty and increased volatility as investors once again closely watch public health updates arriving hour by hour, analysts said.After a solid rally on Monday — the S&P 500 rose 1.3 percent, recovering some of the ground lost in a panicky slide on Friday — global markets were sliding again on Tuesday. In New York, the S&P 500 opened sharply lower amid new con …
