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The U.S. will spend $3 billion on developing antiviral pills to treat Covid-19.

The C.D.C. designates the Delta version of the virus a ‘variant of concern.’

The C.D.C. says the Delta virus variant is now a ‘variant of concern.’

The C.D.C. names the contagious Delta virus is now a ‘variant of concern,’ the C.D.C. said.

The contagious Delta strain is now a ‘variant of concern,’ the C.D.C. said.

Deaths of younger people from Covid-19 have upended Hispanic American families.

Novavax offers the U.S. a fourth vaccine. But it might be needed more elsewhere.

When will you need a Covid-19 booster shot?

Moderna applies for full F.D.A. approval for its Covid vaccine.

U.S. experts press calls for China to allow deeper inquiries into the pandemic’s origins.

One vaccine side effect has amplified a concern about birth control: Why isn’t the pill safer?

Chinese masks are driving U.S. companies out of business.

Once a moon shot, 70 percent Covid vaccination may be in reach, poll finds.

Many scientists welcomed Biden’s call for a rigorous inquiry of a Chinese lab, but they said the theory remained unlikely.

President Biden calls for U.S. intelligence agencies to investigate the origins of the virus.

Biden calls for U.S. agencies to ‘redouble’ investigative efforts into the origins of the virus.

U.S. officials push for a more rigorous investigation of the source of the virus.

Moderna says that its vaccine is effective for 12- to 17-year-olds and that it will seek F.D.A. authorization.

Children with Covid inflammatory syndrome may overcome their most serious symptoms.

Anxious about returning to the land of small talk? A psychology researcher explains why.