Bulletin of the World Health Organization

The impact of adolescent pertussis immunization, 2004–2009: lessons from Australia

Helen E Quinn & Peter B McIntyre

Volume 89, Number 9, September 2011, 666-674

Table 5. Incidence rate ratios (IRR)a for pertussis notifications in infants aged less than 6 months during epidemic periods,b by jurisdictional group, Australia, 2004–2009

Jurisdictional groupingc Pre-programme epidemic rated (95% CI) IRR (95% CI)
2005–2007 2008–2009
Australian Capital Territory/ South Australia/Victoria 216.8 (185.1–253.9) 0.20 (0.15–0.28) 1.25 (1.02–1.53)
New South Wales 268.4 (236.0–305.1) 0.60 (0.50–0.73) 2.82 (2.42–3.28)
Western Australia 536.8 (421.8–683.3) 0.18 (0.12–0.27) 0.40 (0.28–0.57)
Queensland 255.1 (214.1–304.0) 0.37 (0.28–0.50) 1.07 (0.85–1.36)
National 251.4 (225.1–280.6) 0.39 (0.33–0.45) 1.62 (1.43–1.84)

CI, confidence interval.

a These represent the ratios given by dividing the notification rate during each of the two epidemic periods after diphtheria, tetanus and acellular pertussis vaccine programme roll-out by the notification rate during the most recent epidemic period before programme roll-out.

b The recent epidemic periods used in the analysis were as follows: Australian Capital Territory, 2003; South Australia, 2001; Victoria, 2001/2002; New South Wales, 2000/2001; Queensland, 2001/2002; Western Australia, 2004; national, 2001.6

c Jurisdictional groupings were based on programme delivery characteristics.

d Per 100 000 population.