Substantial Influenza Vaccine Effectiveness in Households With XXXX During the 2013-2014 Influenza Season, When 2009 Pandemic @entity778 Predominated.

@entity1 @entity778 @entity689 @entity683 @entity281
BACKGROUND: We examined the @entity683 vaccine effectiveness (VE) during the 2013-2014 @entity683 season, in which 2009 pandemic @entity778 ( @entity683 A[H1N1]pdm09) predominated. In 2 previous years when @entity778 predominated, the VE was low and negatively affected by prior year vaccination. METHODS: We enrolled and followed 232 households with 1049 members, including 618 @entity1 ; specimens were collected from subjects with acute respiratory illnesses. The VE in preventing laboratory-confirmed @entity281 was estimated in adjusted models. Preseason hemagglutination-inhibition and @entity689 -inhibition antibody titers were determined to assess susceptibility. RESULTS: Influenza A(H1N1)pdm09 was identified in 25 households (10.8%) and 47 individuals (4.5%). Adjusted VE against @entity281 with @entity683 A(H1N1)pdm09 was 66% (95% confidence interval [CI], 23%-85%), with similar point estimates in @entity1 and adults, and against both community-acquired and household-acquired @entity281 . VE did not appear to be different for live-attenuated and inactivated vaccines among @entity1 aged 2-8 years, although numbers were small. VE was similar for subjects vaccinated in both current and prior seasons and for those vaccinated in the current season only; susceptibility titers were consistent with this observation. CONCLUSIONS: Findings, including substantial significant VE and a lack of a negative effect of repeated vaccination on VE, were in contrast to those seen in prior seasons in which @entity778 predominated.
