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It has been more than a year since the World Health Organization declared an end to the COVID-19 public health emergency. But while the virus no longer qualifies as a crisis, experts say it will only stay under control if people get vaccinated.

"Population immunity has moved us out of the pandemic," said Dr. Manisha Patel, chief medical officer for the Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases. "Now the goal is to make sure we keep that immunity up because it does wane. And the way we keep it up is through vaccination. That is the safest way to keep our country healthy."

The CDC that new COVID-19 vaccines would be available later this year. The agency recommends everyone – with the exception of babies under 6 months old – get vaccinated to protect against serious illness this fall and winter. The recommendation applies to people who have previously been vaccinated as well as to those who have never had a COVID-19 vaccine.

People who can wait three months before getting vaccinated, the CDC says. However, certain people may consider getting the vaccine sooner, including those at risk for severe COVID-19.

"Since the 2024-2025 COVID vaccines won't be available until the early fall, it is still fine to get the 2023-2024 vaccine for people who need to be protected now," Patel said.

The CDC also updated its vaccine recommendations for the flu and respiratory syncytial virus, or RSV, as it gears up for the spread of respiratory infections that typically starts in the fall.

"These are some of the most commonly circulating viruses and they start to peak in the fall and winter season," Patel said. "We time the release of the vaccines to make sure people are getting optimum protection."

In the U.S., 81% of adults have had at least one dose of a COVID-19 vaccine, but only 21% got the updated 2023-24 vaccine, according to CDC data. Only 9% said they would definitely get the 2023-24 vaccine, and 43% said they probably or definitely would not.

That could leave many people unprotected against currently circulating strains of the virus, said Dr. Hung Fu Tseng, a research scientist at the Kaiser Permanente Department of Research and Evaluation and a professor at the Kaiser Permanente Bernard J. Tyson School of Medicine in Pasadena, California.

"Our protection goes away over time," he said, adding that a regular vaccine dose is needed to keep that protection.

Like the flu vaccine, COVID-19 vaccines will offer protection against currently circulating variants during the fall and winter, Patel said. "They should protect you through the season."

The main goal of vaccination – for any virus – is not to completely prevent infection but to reduce disease severity if an infection occurs, Tseng said. "The goal is to prevent severe outcomes, especially for the elderly, immune-compromised people and infants."

Studies show those protections peak in the early weeks following flu and COVID-19 vaccination and then slowly wane, but remain effective for five months or longer.

Vaccines can "bring the disease from wild to mild," Patel said. Whether they prevent someone from developing symptoms depends on numerous factors, including age and whether the person has any underlying conditions.

COVID vaccination clearly makes a difference in disease severity and the risk of being hospitalized, even in younger adults. CDC data shows that 78% of adults under 50 who were hospitalized because of COVID-19 from October 2023 to March 2024 had not received a bivalent booster introduced in 2022 or a 2023-24 vaccine. Overall, only 11% of adults hospitalized for COVID-19 had received a 2023-24 vaccine prior to being hospitalized.

People with cardiovascular disease, which includes heart disease and stroke, are at especially high risk. Federal data shows it is the most common underlying condition shared by adults ages 50 and older who end up in the hospital because of COVID-19. "The best way to protect them is getting their COVID-19 shot," Patel said.

Having cardiovascular disease increases the risk of disease severity for all three viruses, Patel said. People 50 and older with coronary artery disease are 2.4 times more likely to be hospitalized with RSV than people without coronary artery disease, CDC data shows. And studies have linked both RSV and the flu to an increased risk for heart attacks and strokes, especially among older adults.

The that adults who did not get an RSV vaccine last year get one this year if they are 75 and older or if they are 60 to 74 and at increased risk of severe disease because they either live in a nursing home or have a chronic medical condition, such as lung or heart disease.

Patel said it's still unclear how long protection from an RSV vaccine lasts and that the question is being studied. "But at this point, we do not have the data to suggest that revaccination is needed right now."

However, people should get flu and COVID-19 vaccines annually because these viruses change slightly each year and the vaccines are adjusted to better fight new variants, Patel said. As with the COVID-19 vaccine, the CDC recommends for anyone 6 months and older, with rare exceptions.

While the 2024-25 COVID-19 vaccine likely won't be available until September or October – and can be given at the same time as the flu vaccine – the RSV vaccine has not changed since last year and may be taken slightly earlier, toward the end of August, Patel said.

The best time to get a flu vaccine is September or October, with a few exceptions, the CDC says. Pregnant women in their third trimester are encouraged to get vaccinated in July or August to protect their unborn child from the flu during the first few months of life, when they are too young to get vaccinated.

Tseng said these vaccines are generally safe and encouraged anyone eligible to get them. "Unless you are certain you might be allergic to an ingredient in the vaccine, there's no reason you shouldn't receive them," he said.

Editor's note: This story was corrected on Aug. 9, 2024. An earlier version of this story incorrectly stated that the World Health Organization had declared an end to the COVID-19 pandemic. On May 5, 2023, WHO announced the pandemic no longer fit the definition of a "public health emergency of international concern."