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.

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.

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.

In Louisiana, Vaccine Misinformation Has Public Health Workers Feeling ‘Stuck’

Facing deep mistrust stoked by rampant conspiracy theories, local health officials are fighting for influence when the only sure strategy for beating back the virus is getting more people vaccinated.

Opinion | American Dysfunction Is the Biggest Barrier to Fighting Covid

Lax vaccination and haphazard rules on masking sabotage the fight against the Delta variant in the U.S.

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.

Outbreaks of Untreatable, Drug-Resistant Fungus Spread in 2 Cities

For the first time, the C.D.C. identified several cases of Candida auris that were resistant to all drugs, in two health facilities in Texas and a long-term care center in Washington, D.C.

‘Not Out of the Woods’: C.D.C. Issues Warning to the Unvaccinated

The renewed sense of urgency was aimed at millions of people who have not yet been vaccinated and therefore are most likely to be infected.

‘Not Out of the Woods’: C.D.C. Issues Warning to the Unvaccinated

The renewed sense of urgency was aimed at millions of people who have not yet been vaccinated and therefore are most likely to be infected.

Why Vaccinated People Are Getting ‘Breakthrough’ Infections

The vaccines are effective at preventing serious illness and death, but they are not a golden shield against the coronavirus.

C.D.C. Director Warns of a ‘Pandemic of the Unvaccinated’

Cases, hospitalizations and deaths remain far below last winter’s peak, but the director urged people to get fully vaccinated.

F.D.A. Attaches Warning of Rare Nerve Syndrome to Johnson & Johnson Vaccine

Federal regulators concluded that the risk of developing the syndrome was low, and that the benefits of the vaccine still strongly outweigh it.

Guillain-Barré and Vaccines: What You Need to Know

The link between the rare neurological disorder and the Johnson & Johnson Covid-19 vaccine may be real, but the risk appears to be very small.

U.S. Officials Press Pfizer for More Evidence of Need for Booster Shot

After meeting with company representatives, officials said the decision would depend partly on data on infections in vaccinated people that cause serious disease or hospitalization.

Síndrome Guillain-Barré: qué es y cómo se relaciona con las vacunas

La relación entre este raro trastorno neurológico y la vacuna contra la COVID-19 de Johnson & Johnson puede ser real, pero el riesgo parece ser muy pequeño.

What Parents Need to Know About the C.D.C.’s Covid School Guidelines

The agency’s advice on distancing, masks and vaccination brings the coming school year a bit more into focus.

The C.D.C. Issues New School Guidance, With Emphasis on Full Reopening

The guidance acknowledges that many students have suffered from months of virtual learning.

Why Can’t Europeans Travel to America?

The European Union has reopened to visitors from the United States, but the traffic has not been two-way. There are few clues as to when that will change.

The Real Toll From Prison Covid Cases May Be Higher Than Reported

Some deaths were not counted as part of prison virus tallies because hospitalized inmates were officially released from custody before they died.