Pandemic influenza viruses often cause severe disease in middle-aged adults without preexisting comorbidities. A serum antibody preexisting in middle-aged adults cross-reacts with, but does not protect against, 2009 H1N1 influenza virus. The existence of this antibody may account for the unusual age distribution of severe flu cases during pandemics.
- Ana Clara Monsalvo
- Juan P Batalle
- Fernando P Polack
