Failure to vaccinate or failure of vaccine? Effectiveness of the 23-valent pneumococcal polysaccharide vaccine program in Indigenous adults in the Northern Territory of Australia

Abstract

Over the last decade, there has been no discernible reduction in Invasive Pneumococcal Disease (IPD) amongst Indigenous adults in the Northern Territory (NT) of Australia, despite increasing vaccination coverage. We examined the utility of two common methods, the screening method and the indirect method, to determine the 23-valent pneumococcal polysaccharide vaccine effectiveness (VE) in prevention of IPD amongst Indigenous adults in this setting. VE was calculated for the period 2001-2005 across two distinct geographical areas where the disease burden was known to differ. VE against vaccine-type IPD was 3.4% (95% CI -43, 35) for the NT. However, population vaccination coverage varied widely..