There is some good news for those who got the flu shot during this season: The formulation of this year looks to be effective in preventing hospitalization and severe cases. This is based on the performance of the vaccine in regions where the flu season has ended.
Health officials are looking at how flu vaccines perform in countries of the Southern Hemisphere, where flu season runs from April to September. The CDC published an analysis that examined mid-season data on flu in South America. It showed that the vaccine was more effective than 50% at preventing hospitalizations.
Since the publication of that report earlier this year, it was discovered that the vaccine used in South America became less and less efficient as the flu season progressed. The flu vaccines in the U.S. have been updated to protect against the versions of the virus seen in South America at the end of the flu season.
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“Final estimates may differ from interim estimates. I looked at some final season data last week, and effectiveness dropped later in the season. This is what happens when there are changes in the virus circulating. It was mainly a type of influenza A H1N1, said Annette Regan, PhD, MPH. She is a co-author of the CDC Report on Southern Hemisphere Flu. We have updated the formulation based on this change.
“It was good because it showed us that the vaccine worked really well in the middle and end of season. But when we get to the end, things don’t look the same.” Regan, a former flu researcher for the CDC in Australia and the CDC in the Northern Hemisphere, said that the formulation used in the Northern Hemisphere is slightly different from what was used in South America. She is now an Associate Professor at the University of San Francisco Orange County Campus.
The Pan American Health Organization (PAHO), a regional office of the World Health Organization for the Americas, has a flu surveillance epidemiologist who tracks flu trends south of the equator. This helps prepare medical teams and officials for the flu season in the north.
She said that the interim report, which was based on data from Argentina, Brazil, Chile, Paraguay, and Uruguay, could help in preparations, such as estimating the season’s need for health services and also demand for antiviral medications used to treat influenza.
Couto, a coauthor of the CDC report, said: “Of course influenza is a tricky, pandemic virus. It may not be the same between hemispheres, but we’re always on alert and monitoring these viruses.”
In the United States, there is no official date to start the flu season. It is not always easy to determine the exact start date because it is usually decided afterward, depending on factors like increasing hospitalizations and positive flu tests. This usually happens in late November.
Regan said that the flu season in the U.S. tends to start in the Southeast states like Florida, Texas, and the surrounding areas, then spread from there. Regan said that the flu season usually does not last long. “We’re talking about a few weeks at most,” she said.
The U.S. is on the cusp of a flu season.
According to the latest Weekly Flu Report, the CDC reported that influenza cases were on the rise throughout the Southeast as well as the South Central region and West Coast. Nationally, approximately 4% of all flu tests come back positive. One child has already died from influenza. Regan pointed out that children are among the groups who have low vaccination rates for flu in the U.S.
She said, “I don’t believe any child should die of flu in 2023 if we can avoid it.”
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The CDC recommends that everyone aged six months or older in the U.S. get vaccinated against the flu. Regan explained that it takes about two weeks for the body to produce enough antibodies to provide maximum protection. The effectiveness of the vaccine is usually at least four months. The flu is on the rise, so now is the best time to get a shot.
According to the CDC, about one-third (33%) of U.S. children and adults have received a flu shot this year. This is a significant drop in comparison to last year. Adult vaccination rates vary from state to state and can range from 22% to 50%. Flu season severity can vary. However, federal data shows that there are between 9 and 41 million cases of influenza each year, up to 710,000 hospitalizations, and between 12 and 52,000 deaths.
The CDC estimates between October 1 and November 11 of this year that there were:
- Flu cases range between 780,000 and 1,6 million
- Between 360,000 and 770,000 flu-related medical visits
- Hospitalization for 8,000 to 17,000 patients
- There are between 490 and 1500 flu deaths
The COVID-19 Pandemic has disrupted seasonal trends in flu, leading to lower-than-normal flu cases during a time when quarantines and stay-at-home orders were common. The flu returned last winter with a vengeance. Couto and Regan both said that all signs point to a return to normalcy this season.
The risk of death or serious illness from influenza remains, especially among high-risk groups like older people and very young children. Regan encouraged people to take other steps to prevent the spread, even if the vaccine has been received, in order to protect not only themselves but also those who are at risk, such as grandparents or newborns.
Regan explained that vaccines are not 100% effective. It is, therefore, important to wash your hands and cover your mouth when you sneeze or cough.
Many data show how influenza is spread among children very well. “Keeping them at home when they are sick can help to control the spreading of influenza and RSV and stop these epidemics,” said she.
Regan and Couto agreed that it does not matter if this season of flu is returning to normal or if predictions are accurate; the actions each individual takes – such as getting vaccinated or washing their hand – are important.