No evidence of increasingHaemophilus influenzaenon-b infection in Australian Aboriginal children

Abstract

BackgroundHigh, or increasing, rates of invasive Haemophilus influenzae (Hi) type a disease have been reported from North American native children from circumpolar regions, raising the question of serotype replacement being driven by vaccination against Hi type b (Hib). Indigenous Australians from remote areas had high rates of invasive Hib disease in the past, comparable to those in North American Indigenous populations.ObjectiveEvaluate incidence rates of invasive Hi (overall and by serotype) in Indigenous Australian children over time.DesignDescriptive study of Hi incidence rates by serotype, in the Northern Territory (NT) and South Australia (SA) from 2001 to 2011. Comparison of NT data with a study that was conducted in the NT in 1985–1988, before Hib vaccine was introduced.ResultsThe average annual rate of invasive Hi type a (Hia) disease in Indigenous children aged <5 years was 11/100,000 population. Although the incidence of Hi infection in Indigenous children in 2001–2003 was lower than during 2004–2011, this may be due to changes in surveillance. No other trend over time in individual serotypes or total invasive Hi disease, in Indigenous or non-Indigenous people, was identified. Compared to 1985–1988, rates in 2001–2011 were lower in all serotype groupings, by 98% for Hib, 75% for Hia, 79% for other serotypes and 67% for non-typeable Hi.ConclusionsThere is no evidence of increases in invasive disease due to Hia, other specific non-b types, or non-typeable Hi in Australian Indigenous children. These data suggest that the increase in Hia some time after the introduction of Hib vaccine, as seen in the North American Arctic Region, is not common to all populations with high pre-vaccine rates of invasive Hib disease. However, small case numbers and the lack of molecular subtyping and PCR confirmation of pre-vaccine results complicate comparisons with North American epidemiology.

Trends in the epidemiology of invasiveHaemophilus influenzaedisease in Queensland, Australia from 2000 to 2013: what is the impact of an increase in invasive non-typableH. influenzae(NTHi)?

“…Because comparative pre-vaccine data for the incidence of encapsulated non-b strains was unavailable, the phenomenon of strain replacement could not be adequately assessed. A recent study by Menzies et al demonstrated no increasing trend in Hia or NTHi in the Indigenous population in South Australia and Northern Territory and overall post-vaccination rates of invasive encapsulated and non-typable disease were lower than pre-vaccination rates in that population [35]. The number of notified cases and rates of Hib Australia-wide plummeted markedly following Hib vaccine introduction [10].…”

Haemophilus influenzae serotype a septic arthritis in an immunized central Australian indigenous child

“…9 However, a recent surveillance study in Australia has failed to demonstrate an increase in invasive Hia since the introduction of the Hib vaccine. 10 An epidemiological calculation of invasive H. influenzae disease in the USA concluded that although the incidence of Hib has fallen in American Indians and native Alaskan children since the introduction of the vaccine, invasive disease has not been replaced by non-Hib serotypes. 11 Our patient responded well to timely surgical intervention and antibiotics, with a significant clinical improvement.…”

Classification, Identification, and Clinical Significance of Haemophilus and Aggregatibacter Species with Host Specificity for Humans

“…An unexpectedly large proportion of invasive childhood infections caused by serotype a was recently reported from several Canadian provinces (205,230) and among Alaska Native children (231). There is no evidence of substantial replacement disease with non-b serotypes in young children in the United States (232) or of increases of non-b infection in Australian indigenous children (233).…”