La variante delta se infiltró en un aula de primaria. Así sucedió

Un detallado estudio realizado en California descubrió que la variante se propagó fácilmente de una profesora no vacunada a los niños y, en algunos casos, a sus familias.

Demand Surges for Deworming Drug for Covid, Despite Scant Evidence It Works

Prescriptions for ivermectin have jumped to more than 88,000 per week, some pharmacists are reporting shortages and people are overdosing on forms of the drug meant for horses.

How the Delta Variant Infiltrated an Elementary School Classroom

A detailed study in California found that the variant easily spread from an unvaccinated teacher to children and, in a few cases, their families.

Pfizer and BioNTech say a third shot boosts antibodies against the virus.

The companies said they will submit their data by the end of the week and ask the F.D.A. to approve a third shot.

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.

Stepping Forward Into Marriage, Round Two

When Mary Elizabeth Williams got back together with her husband, she didn’t expect a cancer diagnosis — or for her story to inspire a television episode.

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.

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

The study is the first real-world test of the vaccine’s efficacy against Delta, a highly contagious variant of the virus surging across the United States and much of the world.

Some Are Chasing Extra Vaccine Shots, While Scientists Debate

Boosters may not be necessary yet, many experts say, and the pursuit of additional shots raises ethical questions.

Citing New Data, Pfizer Outlines Case for Booster Shots

Pfizer’s coronavirus vaccine may become slightly weaker over time, the company reported. But experts said that most people won’t need boosters anytime soon.

ACA opens an investigation into the delay of the second dose of Sputnik V

The Administrative Control Authority (ACA) of the Government of National Unity announced the launch of an inquiry into the delay of the second dosage of

Biden Officials Now Expect Vulnerable Americans to Need Booster Shots

The growing consensus that at least some Americans will need a booster is partly tied to research suggesting that Pfizer’s vaccine is less effective after about six months.

The Beta Variant: What Scientists Know

The variant can dodge some of the immune system’s defenses, but is still vulnerable to vaccines.

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.

BioBonds Would Use Wall St. Tools to Fund Medical Research

Karen Petrou invented a new funding model for curing blindness. Proposed legislation aims to apply it to medical research more generally.

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.

In Reversal, F.D.A. Calls for Limits on Who Gets Alzheimer’s Drug

The agency faced criticism for approving Aduhelm for all Alzheimer’s patients. Now it recommends that the drug be given only to those with mild symptoms.

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

Israel reported that the Pfizer vaccine was 64 percent effective against the Delta variant. Other studies suggest a higher rate.

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.