Questions about novel coronavirus antibodies—whether tests for them are accurate or how well they protect against reinfection—have overlooked another, incredibly important mechanism of human defense. When crucial vaccine data was released this week, the spotlight shifted to this unsung immune player: T cells. AstraZeneca, Pfizer and partner BioNTech, as well as China’s CanSino Biologics all hailed the presence of these white blood cells in vaccine recipients as a sign their shots show promise. T cells are a reminder that the body’s defenses rely on more than one weapon, and that much of the immune response to Covid-19 is still a mystery, especially after researchers said antibodies lack staying power. —David E. Rovella

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Here are today’s top stories

Worldwide confirmed coronavirus infections exceeded 15 million, with more than 4 million of them in America—double that of six weeks ago. As death rates in California and Florida accelerate, the pathogen’s assault on the battered nation is only intensifying.

U.S. jobless claims rose last week for the first time since March, the latest sign that a post-lockdown recovery is slowing as Covid-19 spreads and restrictions are reimposed. Initial claims rose 109,000 to 1.42 million in the week ended July 18. The actual number of people collecting jobless benefits is reportedly a staggering 30 million.

Still, credit-card companies Synchrony Financial, Capital One and Discover said delinquencies have remained low even as unemployment surged. But that likely won’t last.

The U.S. Department of Homeland Security, a huge, relatively new state-security apparatus created after the 9-11 attacks, is peppered with empty leadership positions, run by a former lobbyist who himself is an acting director, and filled with ex-police employees and veterans. Its paramilitary ethos has made it ripe for manipulation, former DHS directors warn. President Donald Trump’s decision to use its agents to assault and detain American citizens, functioning as his own personal militia, could do lasting damage to its actual mission: Stopping terrorism.

Chinese President Xi Jinping has pit his nation not only against the U.S. (while Trump has pit the U.S. against China), but much of the rest of the world, experts say. It’s been a successful strategy for maintaining power domestically, but it may hurt China, and everyone else, in the long run.

Zimbabwe’s president has picked a fight with the country’s most successful businessman, and the economy may end up the loser.

What you’ll need to know tomorrow

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What you’ll want to read in Bloomberg Sports

DraftKings Is Finally Getting Back to Sports

As big-time sports fell away in March, DraftKings and FanDuel hatched crazy ways to entice America’s gamblers: Players could win money on July 4 Google searches for hot dogs versus hamburgers, for example. Now they’re gearing up for the real thing, starting with Major League Baseball’s opening day Thursday, and investors look like the real winners.

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