Pfizer vaccine provides 90 percent protection against hospitalization for six months, study finds.

The findings, which also document a waning of protection against infection, come as officials debate the necessity and timing of booster shots.

Battling Delta, New Zealand Abandons Its Zero-Covid Ambitions

The country is changing course seven weeks into a lockdown that has failed to end the outbreak and tested the patience of many residents.

Is the Coronavirus Getting Better at Airborne Transmission?

The Alpha variant traveled more efficiently in small droplets, two new studies found. The Delta variant may have continued this evolution.

U.S. Coronavirus Death Toll Surpasses 700,000 Despite Wide Availability of Vaccines

The latest Covid-19 deaths were concentrated in the South, and included more younger people than before. Every age group under 55 saw its highest death toll of the pandemic this August.

How Asia, Once a Vaccination Laggard, Is Revving Up Inoculations

Several countries are now on track to surpass the United States in fully vaccinating their populations, lifting hopes of a more permanent return to normality.

Does My Mask Protect Me if Nobody Else Is Wearing One?

Masks work best when everyone in the room has one on, but you’ll still benefit from masking up even when those around you aren’t.

Could This Covid Wave Reverse the Recovery? Here’s What to Watch.

Some businesses are still hurting, and federal aid has wound down. But economists see sources of resilience and signs of strength.

‘I Just Cry All the Time’: Non-Covid Patients Despair Over Delayed Care

In areas inundated with coronavirus patients, hospitals have postponed treatments and surgeries for people with other serious conditions.

Opinion | The World Is at War With Covid. Covid Is Winning.

The world can’t end this pandemic — or prevent the next one — without global vaccine equity.

Does My Mask Protect Me if Nobody Else Is Wearing One?

Masks work best when everyone in the room has one on, but you’ll still benefit from masking up even when those around you aren’t.

Opinion | Why Covid Vaccines for Kids Are Taking So Long

The F.D.A. needs a new system for responding to pandemics.

Opinion | Rich Countries Worry About Booster Shots. They Should Be Worried About Africa.

Just 20 percent of people in low- and lower-middle-income countries have had a Covid-19 vaccine dose — versus 80 percent in richer countries.

U.S. Booster Policy Is in Flux as Studies Add to Dissent

A week before President Biden’s plan is to roll out, scientists are at odds about whether extra coronavirus shots are needed and for whom.

Opinion | Delta Tells the Economy, Not So Fast

The continuing struggles of U.S. cities suggest the worst of the damage is far from over.

In Review, Top F.D.A. Scientists Question Imminent Need for Booster Shots

An article, written with other vaccine experts, put the regulators at odds with key federal health officials, including Dr. Anthony S. Fauci.

Curtains Up! How Broadway Is Coming Back From Its Longest Shutdown.

Determined to reopen, crews are dusting off spotlights, dancers are relearning steps, and everyone is testing, testing, testing as theater seeks to rebound from the devastating pandemic.

In a new review, some F.D.A. scientists and others say boosters aren’t needed for the general population.

The benefits of a third shot for most people are small and are far outweighed by the benefits of using those doses for initial vaccinations, the scientists say.

N.Y.C. Virus Cases Appear to Plateau. Could an Uptick Lie Ahead?

As students head back to school, experts say that the city’s third coronavirus wave may be ebbing.

Biden’s Sweeping Vaccine Mandates Infuriate Republican Governors

Some employers and business groups welcomed the new coronavirus requirements, but many G.O.P. leaders issued outright condemnations.

Federal Research Bolsters the Case for Vaccine Mandates

Scientists believe the administration’s new measures may tamp down the pandemic, although the effects will not immediately be obvious.