Southern Hemisphere Influenza and Vaccine Effectiveness Research and Surveillance

Huang, Qiu Sue; Turner, Nikki; Baker, Michael G; Williamson, Deborah A; Wong, Conroy; Webby, Richard; Widdowson, Marc-Alain

SHIVERS surveillance platforms provided a systematic opportunity to estimate VE for the prevention of general practice visits and hospitalizations for RT-PCR-confirmed influenza from the same population in the same influenza season. 40, 41 A case test-negative control design is used to estimate annual propensity-adjusted vaccine effectiveness in both hospital and community settings. The data in 2013 showed moderate effectiveness of influenza vaccine against medically attended and hospitalized influenza in NZ with 56% (95% CI 34,70) against influenza presenting to general practice and 52% (95% CI 32,66) protection against laboratory-confirmed influenza hospitalization. 41 Immune responses SHIVERS surveillance platforms also provided sera and whole-blood samples during acute and convalescent phases of infection to study humoral and cellular immune responses from a subset of severe (N = 39) and moderate (N = 29) influenza cases in 2013. With these samples, and using a combination of serological and immunological assays, we were able to (a) estimate the relative contribution of early adaptive and cellular immune responses to disease severity; (b) identify differences in the immune profiles between these diseases groups; and (c) identify immunological correlates of disease severity in subpopulations. Data acquired so far indicate that SARI cases may experience a more robust immunologic response during infection (i.e. greater increases in HA-and NA-specific antibody titres as well as magnitude of T-cell response). The ability to parse out immunological differences between severe and moderate influenza cases in this pilot cohort highlights the value of adding the active immunology study to the SHIVERS platforms.