Novel correlates of protection against influenza A(H1N1)pdm virus infection

To assess potential alternative correlates of protection, blood samples from participants in a Nicaraguan household transmission study with confirmed exposure to A(H1N1)pdm virus were tested using the classical HI assay as well as in enzyme-linked immunosorbent assays (ELISAs) that measured antibodies against the full-length HA, the HA stalk domain or the neuraminidase (NA).