Bill Dudley, Bloomberg Opinion Columnist & Former President, Federal Reserve Bank of New York, says there is a risk to the Fed's credibility. Lori Calvasina, RBC Capital Markets Head of U.S. Equity Strategy, says the fear in the markets is really starting to becoming palpable. Andrew Hollenhorst Citi Chief U.S. Economist, says the most important economic mystery right now is what's going on in the labor market. Amber D'Souza, Johns Hopkins University Bloomberg School of Public Health Professor of Epidemiology, says Pfizer's trial data for children is an "exciting development."