Vaccines could be a key means of suppressing bird flu and avoiding the slaughter of millions of chickens, which is blamed for egg prices averaging nearly $6 a dozen. But the move has been delayed in part because of concerns it could jeopardize chicken exports worth billions of dollars a year.

As President Donald Trump showcased Tesla electric vehicles on the South Lawn of the White House on Tuesday, he faced questions about the timing of what is being called a “car commercial.” With stock markets tumbling—taking retirement accounts with them—and some Americans grappling with job uncertainty,