Federal health officials expressed optimism on Tuesday that the nation was better prepared to weather a surge of Covid-19 infections this winter compared with a year earlier, and they renewed their pleas for Americans to get an updated booster shot.

The administration is hopeful that the combination of infections and vaccinations will prevent a repeat of what happened last year.

As families gather for Thanksgiving, the coronaviruses appears to be less of a threat than it was a year ago. Mr. Biden banned travel from eight African nations and sent military medical workers to hospitals that officials feared would be overrun with patients.

The White House's Covid-19 response coordinators said he was confident about the holiday season if Americans continued to get vaccinations. He believes that we can't manage our way through it if people get their vaccine.

That could be a big deal. Weary of two years of repeated vaccine campaigns, Americans have been reluctant to take advantage of the new shots. Only 35 million people have received one of the revised shots. The administration was able to buy more doses than the other way around.

More than 300 Americans a day are still dying of Covid-19, even though federal health officials say nearly every Covid death is preventable through vaccination and treatment. The flu and R.S.V. are resurging after two years of low levels of infections.

The location of the coronaviruses is not known. There is a new subvariant of Omicron called XBB that is being watched by federal officials. In India and Singapore, the new subvariant is showing up in testing of travelers at the nation's major international airports.

  • Long Covid: People who took the antiviral drug Paxlovid within a few days after being infected with the coronavirus were less likely to experience long Covid months later, a study found.
  • Updated Boosters: New findings show that updated boosters by Pfizer and Moderna are better than their predecessors at increasing antibody levels against the most common version of the virus now circulating.
  • Calls for a New Strategy: Covid boosters can help vulnerable Americans dodge serious illness or death, but some experts believe the shots must be improved to prevent new waves.
  • Future Vaccines: Financial and bureaucratic barriers in the United States mean that the next generation of Covid vaccines may well be designed here, but used elsewhere.

Dr. Fauci said that XBB appeared to be very fast at evading the body's first line of defense against the virus, which was created by previous infections or vaccinations. If the immune system fails to block the virus, other parts of the immune system can kick in to help.

Singapore, where XBB led to a jump in infections, did not show a rise in hospitalizations.

Dr. Fauci, who became a household name during the Pandemic and is retiring from government service at the end of the year, used the opportunity to urge Americans to get the updated booster shots.

Dr. Fauci said, "My message and my final message is that, please, for your own safety, for that of your family, get your updated Covid-19 shot as soon as you're eligible"

Over the next six weeks, the administration is trying to get the new boosters. $475 million was spent to expand vaccination efforts at community health centers and other locations, and officials are hoping to reach more Americans by airing advertising during the World Cup. If nursing homes don't offer the updated shots, they will face enforcement actions from regulators.

As the Centers for Disease Control and Prevention delivered encouraging news about the effectiveness of the new shots, the push came as a result.

A major new study released by the agency shows that the updated shots bolster protection against disease by 28 to 56 percent, depending on a person's age and how long they've had the shot. The researchers found that people who waited longer got more benefits from the revised boosters.

This is a home run. The Food and Drug Administration pushed for the development of the new booster shots.

The study looked at 360,000 people who reported Covid-19 symptoms between September and November. The significance of it is limited by the fact that the Omicron subvariant that accounted for the largest number of infections during that period has gone away.

Pei-Yong Shi, a virologist at the University of Texas Medical Branch who has conducted laboratory studies of the updated boosters, said that the variant in the real world have already moved on.

Dr. Shi said it was difficult to measure how well the updated boosters worked because so many people had immunity from earlier infections. Estimates of the effectiveness of the shots can be made low by that.

The C.D.C. study showed that the revised boosters were worth the money.

The new shots appeared to provide moderate protection against disease, but it was not clear how long the protection would last.

The researchers didn't show whether the updated boosters worked better than the original ones, a swap that cost the federal government a lot. He said that he didn't think there would have been much difference.

Federal officials are not the only ones who are cautiously optimistic that Americans will shift indoors over the winter. The doctor said he didn't expect the virus to cause as much suffering and death this winter as it did last year.

The effectiveness of Paxlovid was underscored in a study released by the C.D.C. on Tuesday.

The study found that people who were prescribed Paxlovid had a lower hospitalization rate than people who weren't. More than half a million people who did not receive Paxlovid were compared with 200,000 adults who did. Both groups had been exposed to the coronaviruses.

Only a small percentage of those eligible for Paxlovid were prescribed it. People with multiple underlying health conditions should be offered the medication, according to the researchers. A question that makes providers wonder if the course of treatment is long enough is how often Covid symptoms come back after five days of treatment.

Kody Kinsley is the top health official in North Carolina. Roughly two-thirds of adults in his state were at high risk of severe disease from the coronaviruses, but doctors were reluctant to prescribe Paxlovid to them.

"This has been a perennial issue and something we've been pretty vocal about." I am not sure if you need it.

The decision to take Paxlovid should be based on how vulnerable a patient is to a serious case of Covid-19.

Zolan Kanno-Youngs reported.