Long-term trends in invasive Haemophilus influenzae type B disease among indigenous Australian children following use of PRP-OMP and PRP-T vaccines.

BACKGROUND

Among indigenous populations with high incidence and early onset of invasive Haemophilus influenzae type b (Hib) disease, PRP-OMP vaccines are used in the United States and PRP-T vaccines in Canada. In Australia, PRP-OMP vaccines were exclusively used in indigenous children from 1993 until they were replaced by PRP-T between late 2005 and 2009.

METHODS

Analytic descriptive study of 20 years of enhanced surveillance data (1993-2013) for invasive Hib disease in Australian children <10 years of age was conducted.

RESULTS

Of 579 Hib cases under 10 years of age reported from vaccine introduction in 1993 to 2013, 78 (13%) were in indigenous children, 47 (60%) of whom lived in regions with high prevaccine incidence. In this population, incidence per 100,000 declined from 18.1 (95% confidence interval [CI]: 10.4, 29.4) in the early PRP-OMP period (1993-1996) to 6.2 (95% CI: 4.0, 9.2) and 4.7 (95% CI: 1.7, 10.3) in the later PRP-OMP (1996-2009) and PRP-T periods (2009-2013), respectively. The indigenous:nonindigenous incidence rate ratio increased to 43 (95% CI: 16, 145) and 58 (95% CI: 7, 2660) in the later PRP-OMP and PRP-T periods, respectively, more than 10-fold higher than in lesser-incidence Australian regions.

CONCLUSIONS

We found no change in Hib incidence among indigenous Australian children living in high-incidence regions in the first 4 years following a change to PRP-T-containing combination vaccines. This may be of relevance to North American indigenous populations characterized by suboptimal living conditions and young age of onset for whom PRP-OMP continues to be recommended, such as Alaska Natives.