What Causes Canker Sores? (Published 2018)

Medical experts still don’t know the precise cause of canker sores, though anyone can get them.

Extra Shots from J. & J. and Pfizer Give Immune Boost, Companies Report

The Food and Drug Administration will evaluate the new data as the Biden administration pushes a booster shot strategy.

Extra Shots from J. & J. and Pfizer Give Immune Boost, Companies Report

The Food and Drug Administration will evaluate the new data as the Biden administration pushes a booster shot strategy.

A Never-Before-Seen System For Burning 'Deep Fat' Has Been Found in Mouse Studies

A series of new experiments on mice have revealed a key process by which the brain and immune system communicate to burn deep stores of visceral fat.

Vaccine Effectiveness Against Infection May Wane, C.D.C. Studies Find

Federal health officials said the new data justified a campaign of booster shots. But some scientists disagreed, saying not every American needs another dose.

C.D.C. Panel Recommends Third Dose of Covid Vaccine for Immunocompromised

A day after the F.D.A. authorized third doses of the Pfizer-BioNTech and Moderna vaccines for some immunocompromised people, an independent expert panel advising the C.D.C. recommended the move.

F.D.A. to Authorize Third Vaccine Dose for People With Weak Immune Systems

The decision to expand the emergency use of both the Pfizer-BioNTech and Moderna vaccines is meant to help transplant recipients and others whose immune systems are similarly compromised.

What to Know About Breakthrough Infections and the Delta Variant

Scientific understanding of the coronavirus variant is changing quickly. Here’s a recap of the most important findings.

F.D.A. Aiming to Speed Extra Vaccine Doses for Immunocompromised Patients

Worried about a vulnerable population as the Delta variant surges, administration officials are taking a new tack.

F.D.A. Aiming to Speed Extra Vaccine Doses for Immunocompromised Patients

Worried about a vulnerable population as the Delta variant surges, administration officials are taking a new tack.

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

The C.D.C.’s new masking advice was based in part on data showing that the virus can thrive in the airways of vaccinated people. The findings are expected on Friday.

As Infections Rise, C.D.C. Urges Some Vaccinated Americans to Wear Masks Again

In communities with growing caseloads, vaccinated and unvaccinated people should return to wearing masks indoors in public areas, health officials said.

Why Everyone Has the Worst Summer Cold Ever

As pandemic restrictions begin to relax, common viruses that cause drippy noses, stuffy heads and other cold symptoms have roared back to taunt your immune system.

J.&J. Vaccine May Be Less Effective Against Delta, Study Suggests

Many who received the shot may need to consider boosters, the authors said. But federal health officials do not recommend second doses.

You’re Missing Microbes. But Is ‘Rewilding’ the Way to Get Them Back?

The science behind the idea of restoring the intestinal microbiome to an ancestral state is shaky, skeptics say, and in some cases unethical.

Covid Is Especially Risky for People With H.I.V., Large Study Finds

An H.I.V. infection increases the odds of dying from Covid-19 by at least 30 percent, researchers said.

Delta Variant Widens Gulf Between ‘Two Americas’: Vaccinated and Unvaccinated

Data from overseas, particularly Britain, suggest the spread of the virus will set vaccinated and unvaccinated communities on very different paths.

Molecules Produced by Gut Bacteria Could Help The Human Body Fight Cancer

Our guts are fabulous places, filled with a myriad of microbes. These tiny life forms help us with everything from fermenting fiber to feeling full. But their effects don't stay just in the gut.

Citing the Delta Variant, Pfizer Will Pursue Booster Shots and a New Vaccine

Scientists were critical of the announcement, pointing to evidence that the current two-dose regimen is powerfully effective against the coronavirus.

Should People With Immune Problems Get Third Vaccine Doses?

France is handing out third shots of the two-dose vaccines to cancer patients and others with immune system impairments. In the United States, patients like these are on their own.