US Flu Positivity Hits 3.6% as Drifting H1N1 Drives Early Fall Surge
Updated
Updated · Scientific American · Oct 16
US Flu Positivity Hits 3.6% as Drifting H1N1 Drives Early Fall Surge
3 articles · Updated · Scientific American · Oct 16
Summary
CDC data show U.S. flu positivity reached 3.6% by Oct. 9, up sixfold from 0.6% a year earlier after activity began climbing in early September.
Region 9—Arizona, California, Hawaii and Nevada—hit 9.5% positivity, and 98.4% of recent positive tests were H1N1, suggesting the early rise is concentrated and strain-specific.
Experts say the circulating H1N1 has undergone antigenic drift, making it different from prior strains and the vaccine strain and potentially better able to evade existing immunity.
Researchers still say it is too early to judge how severe the winter season will be or how well current shots will perform, but they recommend vaccination now, before Thanksgiving at the latest.
Moderna's mFLUSIVA—the first mRNA seasonal flu vaccine, approved Aug. 5 for adults 50 and older—was 26.6% more effective than a standard shot in Phase 3, though access remains limited.