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Behind the Masks, a Mystery: How Often Do the Vaccinated Spread the Virus?

Citing new data, Pfizer outlined a case for booster shots, but there’s a debate over whether they’re needed.

The American Academy of Pediatrics recommends universal masking in schools this fall.

Fitbits Detect Lasting Changes After Covid-19

C.D.C. advisers are expected to discuss rare heart problems in vaccinated younger people.

C.D.C. Will Not Investigate Mild Infections in Vaccinated Americans

C.D.C. Will Not Investigate Mild Infections in Vaccinated Americans

The virus is an airborne threat, the C.D.C. acknowledges.

When do we have to wear a mask outside? The C.D.C. says less often, and here’s how and why.

Fauci and other top U.S. health officials stress the urgency of vaccinations and their safety.

Patients With Long Covid Face Lingering Worrisome Health Risks, Study Finds

Patients With Long Covid Face Lingering Worrisome Health Risks, Study Finds

Has the Era of Overzealous Cleaning Finally Come to an End?

Why It Pays to Think Outside the Box on Coronavirus Tests

Why It Pays to Think Outside the Box on Coronavirus Tests

Three Feet or Six? Distancing Guideline for Schools Stirs Debate

C.D.C. Traces Covid Outbreaks in Gyms, Urging Stricter Precautions

A Few Covid Vaccine Recipients Developed a Rare Blood Disorder

Virus Variant First Found in Britain Now Spreading Rapidly in U.S.

Twins with Covid Help Scientists Untangle the Disease’s Genetic Roots