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Feeling Terrible After Your Covid Shot? Then It’s Probably Working.

U.S. Health Officials Urge Vigilance as Ebola Spreads in Uganda

The Coronavirus Has Infected More Than Half of Americans, the C.D.C. Reports

Inside a Campaign to Get Medicare Coverage for a New Alzheimer’s Drug

Trying to Solve a Covid Mystery: Africa’s Low Death Rates

Moderna says its booster significantly raises the level of antibodies to thwart Omicron.

Most Covid Vaccines Will Work as Boosters, Study Suggests

Regeneron says its antibody treatment may not be as effective against Omicron, but testing is underway.

Antiviral Covid Pills Are Coming. Will There Be Enough Tests?

New Virus Variant Stokes Concern but Vaccines May Still Work

Pfizer Says Its Antiviral Pill Is Highly Effective in Treating Covid

Has the Virus Infected Huge Numbers of Younger Children?

Pregnant and breastfeeding women are slower to respond to vaccination, researchers report.

Mix-and-Match Covid Boosters: Why They Just Might Work

What Scientists Know About the Risk of Breakthrough Covid Deaths

If You’ve Had Covid, Do You Need the Vaccine?

They Shunned Covid Vaccines but Embraced Antibody Treatment

Second Dose of J. & J. Vaccine Gives Strong Boost, Company Reports

Second Dose of J. & J. Vaccine Gives Strong Boost, Company Reports

What to Know About Breakthrough Infections and the Delta Variant