Flu shots are tied to fewer severe outcomes in both older adults and children, according to two studies presented at IDWeek 2026 in Washington, DC. The findings add fresh real-world evidence that seasonal influenza vaccination keeps people out of intensive care and the emergency department.
The first study, a retrospective cohort analysis from Geisinger Health System, looked at adults aged 65 and older who came to the emergency department with PCR-confirmed influenza. Patients who had been vaccinated at least 14 days before showing up were less likely to end up admitted to the intensive care unit than those who had not received the shot.
The study covered the period from Oct 1, 2024, to April 30, 2025, a full flu season of emergency department visits. Because it used PCR confirmation, the researchers were certain each case was genuine influenza rather than a look-alike respiratory infection, which makes the association between flu shots and milder outcomes harder to dismiss.
The second study came from the CDC VISION Network, which tracks vaccine effectiveness through electronic health records. Its analysis estimated that the 2025-2026 seasonal vaccines reduced influenza-associated emergency department and urgent-care visits among children and adolescents by 36 percent.
Both studies were presented on Oct 23, 2026, at IDWeek, the annual meeting of the Infectious Diseases Society of America. Together, they give doctors and pharmacists new numbers to share with patients who are on the fence about this season’s flu shots.
What the Geisinger flu shots study found
The Geisinger research focused on the group that flu hits hardest: older adults. People over 65 account for most flu hospitalizations and deaths each year, so any intervention that keeps them out of the ICU matters. The flu shots studied were the standard seasonal vaccines given during the 2024-2025 season.
By counting only patients vaccinated at least 14 days before their emergency department visit, the study made sure the vaccine had time to generate an immune response. Patients inside that window were compared with unvaccinated patients who arrived with confirmed influenza, and the vaccinated group had fewer ICU admissions.
Retrospective studies cannot prove cause and effect the way a randomized trial can, but they measure what actually happened across a large health system. Health systems like Geisinger see thousands of flu cases each season, giving the data real weight.
The finding lines up with what flu researchers have long said: the vaccine does not always stop infection, but it often blunts the worst of it. For older adults, that difference can be the difference between a hospital stay and a week recovering at home.
How flu shots cut child ER visits by 36 percent
The CDC VISION Network analysis took a different approach. Instead of one health system, it drew on electronic health records across its network sites to estimate how well the 2025-2026 vaccines worked for children and adolescents.
Its estimate: a 36 percent reduction in influenza-associated emergency department and urgent-care encounters. In plain terms, children who got their flu shots were substantially less likely to end up in an emergency department or urgent-care clinic with the flu than children who did not.
Pediatricians often hear from parents who wonder whether the shot is worth the trouble when children usually recover quickly. The 36 percent figure answers that question with data from the current season rather than theory. Fewer emergency visits mean fewer frightened families, fewer missed school days and fewer chances for a routine infection to turn into pneumonia or another complication.
The analysis covers the 2025-2026 season, so the number reflects the vaccines now in pharmacies and clinics.
What the findings mean for this season
The CDC continues to recommend annual flu vaccination, ideally by the end of October, before the virus gets its seasonal foothold. The new studies give that recommendation fresh backing from data gathered in American emergency departments and health records.
For older adults, the Geisinger results argue for getting flu shots even late in the season, since the protection measured was against the outcome that matters most: intensive care. For parents, the VISION Network’s 36 percent reduction is a concrete reason to give children flu shots rather than gamble on a mild illness.
Flu season typically peaks between December and February, and it takes about two weeks after vaccination for protection to build. The two studies, presented Oct 23 at IDWeek 2026, land just as the window for ideal timing is closing.