Invasive pneumococcal disease in Indigenous people in north Queensland: an update, 2005-2007

To examine trends in invasive pneumococcal disease (IPD) in Indigenous people in north Queensland following the introduction of the 7-valent pneumococcal conjugate vaccine (7vPCV).

Trends in IPD were compared over three 3-year periods: before the introduction of 7vPCV for Indigenous children (1999-2001), and two consecutive periods after its introduction (2002-2004 and 2005-2007).

Incidences of IPD in Indigenous children and adults in 1999-2001 and 2005-2007; trends in IPD caused by 7vPCV and non-7vPCV serotypes; and trends in indirect protective effects and emergence of non-7vPCV serotype IPD.

From 1999-2001 to 2005-2007, there was a 60% decline in IPD, with the virtual elimination of 7vPCV serotype IPD in young (< 5 years) Indigenous children. There is no evidence yet of an increase in non-7vPCV serotype IPD in these children. Although the annual incidence of IPD in Indigenous adults remained virtually unchanged, there was a 75% decline in 7vPCV serotype IPD in these adults (chi2(trend) = 11.65, P < 0.001). However, the incidence of IPD caused by non-7vPCV serotypes more than tripled in adults (chi2(trend) = 7.58, P = 0.006). Serotype 1 IPD has been prominent over the 9 years, but there is no evidence of a recent increase in serotype 19A IPD.

Vaccinating Indigenous children with 7vPCV has protected Indigenous adults in north Queensland through an indirect "herd immunity" effect. However, this benefit has been offset by a recent increase in non-7vPCV IPD in Indigenous adults. Newer pneumococcal conjugate vaccines could prevent, both directly and indirectly, a considerable amount of the persisting IPD in Indigenous people in the region.