Design: 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).
Main outcome measures: 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.
Results: 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 (χ2trend = 11.65, P < 0.001). However, the incidence of IPD caused by non-7vPCV serotypes more than tripled in adults (χ2trend = 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.
Conclusions: 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.
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