Everybody 6 months and older should get at least one dose of the vaccines, the panel said.

Scientific advisers to the Centers for Disease Control and Prevention recommended on Tuesday that all Americans 6 months and older receive at least one dose of the latest Covid shots, the last of a trifecta of vaccines intended to prevent a wave of respiratory infections this fall and winter.

The Food and Drug Administration on Monday approved reformulated Covid vaccines by Pfizer-BioNTech and Moderna. Assuming that Dr. Mandy Cohen, the new C.D.C. director, endorses the scientific panel’s recommendations, large pharmacies will likely have the new shots available later this week.

Vaccines against flu and the respiratory syncytial virus are already on the shelves. The flu vaccine is recommended for everyone 6 months and older, and the R.S.V. vaccine for everyone 60 and older, in consultation with a health care provider.

Some advisers said on Tuesday that they were unsure about recommending the new Covid vaccines to younger adults, or had misgivings about potential side effects, especially in children and young males.

Others worried that endorsing the vaccines for all Americans might undermine messaging about the greater need among those at highest risk from Covid, including older adults.

But the committee ultimately voted to endorse the new vaccines for everyone, citing data presented at the meeting showing short- and long-term risks of Covid at any age.

“It’s clear that vaccination is going to prevent serious illness and death across all age groups,” said Dr. Beth Bell, a professor of global health at the University of Washington.

The panel made recommendations only about the updated Covid shots by Pfizer and Moderna. The timing and number of recommended doses depends on prior immunizations.

The guidelines will be extended to include another vaccine by Novavax and any others authorized by the F.D.A. in the coming months.

“I hope that this will facilitate the availability of the Novavax vaccine once the F.D.A. has reviewed, reviewed and potentially authorized it,” said Dr. Demetre Daskalakis, acting director of the C.D.C.’s National Center for Immunization and Respiratory Diseases.

Pfizer, Moderna and Novavax on Tuesday told the C.D.C. panel that they would charge $120 to $130 per dose for the new Covid vaccines. But the shots will be available at no cost to most Americans until December 2024, through private insurers and a new federal program for uninsured people.

For some Americans, the vaccines cannot come soon enough. Hospital admissions and deaths associated with Covid have been steadily rising since July, although the numbers are still low compared with the same period in other recent years.

Many others now view Covid as only a mild threat. Fewer than half of adults older than 65, and just about one in five American adults overall, opted for the bivalent booster shot offered last fall. (The new shots replace the bivalent booster, which should no longer be used, the panel said.)

The most vulnerable Americans — older adults, immunocompromised people and pregnant women — ought to receive both the Covid and the flu vaccines, experts said. Adults 65 and older accounted for up to 85 percent of flu-related deaths in recent years, according to the C.D.C.

Covid hospitalizations among adults 75 years and older “are consistently two to three times as high as those in the next youngest age group,” who are 65 to 74, according to data presented by Dr. Fiona Havers, who leads the C.D.C.’s surveillance programs for respiratory disease-associated hospitalizations.

Most of those hospitalized adults had multiple underlying conditions, Dr. Havers said. Rates of hospitalization, a proxy for severe illness, are highest among American Indian, Alaska Native and Black Americans.

“African Americans, even from younger ages, have higher incidence of underlying conditions which would lead to higher adverse events in terms of hospitalization, I.C.U. and death,” said Dr. Oliver Brooks, chief medical officer at Watts HealthCare Corporation in Los Angeles. “So definitely the vaccine is needed.”

The new vaccines are designed to target the Omicron variant XBB.1.5, which was the dominant virus when health officials were deciding on the composition of the vaccine.

XBB.1.5 now accounts for only 3 percent of cases, but more than 90 percent of the circulating variants are its close relatives. The new vaccines appear to be effective against all of them, according to data presented at the meeting.

As with the flu vaccine, the greatest benefits of Covid immunization may accrue to those at highest risk. Nonetheless, the shots may help even those at reduced risk recover sooner after an infection, or miss fewer days of work, Dr. Jha said.

Those who have hybrid immunity — from both infection and immunization — have the strongest protection. But immunity of all types wanes over time, according to data presented at the meeting.

Most children and adults hospitalized for Covid since January 2023 had not received the most recent booster shot, Dr. Havers reported.

Even among the relatively young and healthy, Covid poses serious health risks, including long-term effects on the heart and other organs that can emerge and re-emerge months to years after the initial illness, Sharon Saydah, a C.D.C. researcher, told the panel.

Dr. Saydah presented preliminary estimates from the 2022 National Health Interview Survey suggesting that the highest prevalence of post-Covid symptoms occurs among adults aged 35 to 49 years: 9 percent reported health problems at least three months after acute illness.

The percentages of those reporting ongoing symptoms decreases over time, and are lower with the Omicron variant than with previous versions of the virus.

Officials in Britain are offering the new Covid vaccines only to those at high risk, including older adults, those with chronic medical conditions and frontline workers. That decision was based not on calculations about who would most benefit, but because of the prohibitive costs to the British government of offering the shots to everyone, according to Dr. Jha.

For people who are unable or unwilling to make multiple trips to a clinic or pharmacy to space the shots apart, experts recommended getting the shots together. Still, if at all possible, it may be wise to time the shots to provide maximum protection, some experts said.

Influenza typically peaks in February, so “I have generally recommended to people who are elderly to wait until October, just so that they still have a lot more protection,” Dr. Jha said. “You don’t want to get to Halloween and not have taken it, but sometime in October is pretty reasonable.”

Last year, Dr. Jha, who is 52, opted to get the Covid and flu shots at the same time. “I got one in each arm,” he said. “My arms were a little sore for 24 hours, but it was fine.”