Overview
- CDC data show the H3N2 K subclade now accounts for 56% of recent H3N2 detections, with national test positivity up nearly 3% and more than 2,300 hospitalizations reported last week.
- Researchers say the K lineage is genetically different from this season’s vaccine strain, increasing the chance of infections in vaccinated people.
- Early analyses indicate the current vaccines continue to protect against severe outcomes, with stronger effectiveness estimates in children than in adults.
- Vaccine uptake is lagging, including more than 2 million fewer pharmacy-administered doses through October compared with last year and state reports such as just over 20% coverage in Michigan.
- Health experts urge flu shots, early antivirals for high‑risk patients, and basic precautions, as some raise concerns about thinner, delayed surveillance following recent reporting disruptions.