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The Surgeon General said misinformation on social networks is damaging Americans’ health.

Gov. Greg Abbott of Texas says he tests negative for coronavirus.

A guide to vaccine boosters.

See How Vaccines Can Make the Difference in Delta Variant’s Impact

Here’s what to know about breakthrough infections and the Delta variant.

New data suggest J. & J. vaccine works against Delta and recipients don’t need a booster shot.

Some Are Chasing Extra Vaccine Shots, While Scientists Debate

Israeli Data Suggests Possible Waning in Effectiveness of Pfizer Vaccine

Pfizer’s shot remains strong against disease, but Israeli data raise the prospect of it waning against infection.

The world is worried about the Delta virus variant. Studies show vaccines are effective against it.

Zoo Animals Are Getting Experimental Coronavirus Vaccines

Final trial results confirm that CureVac’s mRNA vaccine is far less protective than others.

We’ll Probably Need Booster Shots for Covid-19. But When? And Which Ones?

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

The Pfizer-BioNTech vaccine is incredibly effective against severe disease caused by two variants, studies say.

Moderna booster will be effective against some variants, trial indicates.

The Pfizer-BioNTech vaccine is incredibly effective against severe disease caused by two variants, study says.

The Flu Vanished During Covid. What Will Its Return Look Like?

Plunging Johnson & Johnson Vaccine Supply Dents State Inoculation Efforts