As the current flu season in the United States begins to wind down, health officials say this year’s influenza vaccine performed poorly, with effectiveness rates among the lowest seen in more than ten years.
Experts say the reduced protection was largely due to the emergence of a flu strain early in the winter that was not well matched to the vaccine formula, contributing to a strong wave of infections during the first part of the season.
New data released Friday by the Centers for Disease Control and Prevention shows that visits to doctors’ offices and hospitals for flu-related symptoms continued to decline through last week. The number of states reporting high levels of flu activity has dropped to 16, many located in a region stretching from Colorado across to Virginia.
“The winter respiratory virus season is slowly coming to a close, and we’re all very grateful for that,” said Dr. William Schaffner, a Vanderbilt University vaccine expert.
According to a CDC report published this week, the vaccine used this season was only about 25% to 30% effective in preventing flu-related illnesses serious enough to send adults to a doctor’s office, clinic, or hospital. Among children, those who received the vaccine were about 40% less likely to require medical treatment.
Health officials typically consider flu vaccines successful when they provide between 40% and 60% protection. Based on past CDC research, the effectiveness recorded this season ranks among the lowest levels observed in roughly the last twenty years.
Flu cases surged toward the end of December and were particularly severe in certain regions. Health officials in New York City described the outbreak there as the most intense flu season in two decades.
Relatively low vaccination rates contributed to the situation, but specialists also pointed to the new strain responsible for the majority of infections.
The dominant virus this year belonged to the influenza A H3N2 category. The specific variant, known as subclade K, appeared to spread more easily than other strains, although it did not necessarily lead to more severe illness.
The vaccine designed for this flu season targeted a different version of the H3N2 virus, which may explain why the shot offered less protection, Schaffner said.
CDC researchers estimate that the flu has caused at least 27 million illnesses so far this season, along with approximately 350,000 hospitalizations and 22,000 deaths. At the same point last year, the agency estimated at least 40 million illnesses and 520,000 hospitalizations, though the number of deaths was roughly similar.
At least 101 children have died from flu-related complications this season. Among cases where vaccination status was known, roughly 85% of those children had not been fully vaccinated against influenza.
Although the vaccine does not prevent every infection, it still plays an important role in reducing the risk of severe illness and death, Schaffner said, noting that receiving the flu shot remains beneficial.
CDC figures indicate that vaccination rates among adults have risen slightly this year, reaching 46.5%. The increase follows last year’s particularly severe season, which recorded the highest number of child flu deaths this century.
Among children in the United States, about 48% had received a flu shot by the end of last month. That rate is similar to last year’s level but lower than the approximately 52% vaccination rate recorded at the same point in 2024, according to CDC data.
Since 2010, federal health authorities have recommended annual flu vaccination for everyone six months of age and older. However, in January the Trump administration ended the broad recommendation that all children receive the vaccine, instead stating that the decision should be made by parents in consultation with family physicians.
Meanwhile, preparations are already underway for the next flu season. Last month, the World Health Organization announced its recommended virus strains for vaccines that will be used in the 2026–2027 flu season in the northern hemisphere. The organization said the next vaccines should be designed to protect against subclade K. Earlier this week, an advisory panel at the U.S. Food and Drug Administration endorsed those recommendations.
{Matzav.com}