Name:   CRD - Subject:   OK CRD Date:   5/4/2021 9:09:56 AM

Difficult to answer.  Since the H1N1 is a subtype of Influenza Type A, the serological studies at that time were not specific enough to distinguish H1N1 from antibodies to differing strains of the flu.  As well, since H1N1 affected a primary pediatric population, serology of peds was not routinely performed in order to arrive at a definitive IFR.