FILE - A flu vaccine is readied at the L.A. Care and Blue Shield of California Promise Health Plans' Community Resource Center where they were offering members and the public free flu and COVID-19 vaccines Friday, Oct. 28, 2022, in Lynwood, Calif. Early estimates suggest the flu vaccine performed unusually well in a U.S. winter flu season that has already dissipated, health officials said during a Centers for Disease Control and Prevention vaccines meeting Wednesday, Feb. 22, 2023. (AP Photo/Mark J. Terrill, File)
CNN  — 

Early data from South America shows that the flu vaccine has cut the risk of hospitalization in half this year, a hopeful sign that the vaccine will provide a similar level of protection in the United States as the country heads into its own respiratory virus season.

The Southern Hemisphere typically experiences its flu season a few months earlier than the United States, and trends from that region can help the US prepare for the fall and winter.

This year, mid-season flu vaccine data from five countries – Argentina, Brazil, Chile, Paraguay and Uruguay – shows that vaccination has reduced the risk of hospitalization by 52%, according to a report published Friday by the US Centers for Disease Control and Prevention.

The data are based on about 3,000 patients who were hospitalized between late March and early July. People who had gotten the shot at least two weeks before the onset of symptoms were considered to be vaccinated, and the analysis focused on certain high-risk groups who were prioritized in the vaccination campaigns, including children, people with preexisting conditions and older adults.

So far, the specific virus strains that have been detected in US this year have shown a similar pattern to those that were identified in South America. While these patterns are not yet certain, they offer an “encouraging outlook for vaccine protection” in the Northern Hemisphere, the researchers wrote in the new report.

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For now, Covid-19 remains the dominant respiratory virus that’s circulating in the US. But the CDC has warned that RSV levels are starting to pick up in the South, and flu levels tend to rise starting in the fall.

Annual flu shots are available now and the CDC recommends them for everyone 6 months of age and older in September and October, especially including very young children, people with preexisting health conditions, pregnant people and older adults.

The agency is rolling out new ads it hopes will increase confidence in the vaccines with a clear, straightforward message: The flu vaccine won’t keep a person from getting sick, but it will tame that infection, taking it from “Wild to Mild” — the tagline for the new campaign.

CNN’s Brenda Goodman contributed to this report