Retrospective Case-Control Study of 2017 G2P[4] Rotavirus Epidemic in Rural and Remote Australia

Abstract

Background: A widespread G2P[4] rotavirus epidemic in rural and remote Australia provided an opportunity to evaluate the performance of Rotarix and RotaTeq rotavirus vaccines, ten years after their incorporation into Australia’s National Immunisation Program. Methods: We conducted a retrospective case-control analysis. Vaccine-eligible children with laboratory-confirmed rotavirus infection were identified from jurisdictional notifiable infectious disease databases and individually matched to controls from the national immunisation register, based on date of birth, Aboriginal status and location of residence. Results: 171 cases met the inclusion criteria; most were Aboriginal and/or Torres Strait Islander (80%) and the median age was 19 months. Of these cases, 65% and 25% were fully or partially vaccinated, compared to 71% and 21% of controls. Evidence that cases were less likely than controls to have received a rotavirus vaccine dose was weak, OR 0.79 (95% CI, 0.46–1.34). On pre-specified subgroup analysis, there was some evidence of protection among children <12 months (OR 0.48 [95% CI, 0.22–1.02]), and among fully vs. partially vaccinated children (OR 0.65 [95% CI, 0.42–1.01]). Conclusion: Despite the known effectiveness of rotavirus vaccination, a protective effect of either rotavirus vaccine during a G2P[4] outbreak in these settings among predominantly Aboriginal children was weak, highlighting the ongoing need for a more effective rotavirus vaccine and public health strategies to better protect Aboriginal children.

Characterisation of a G2P[4] Rotavirus Outbreak in Western Australia, Predominantly Impacting Aboriginal Children

“…In addition to the WA outbreak herein described, outbreaks due to G2P[4] were also reported in the Northern Territory (NT) and South Australia [ 3 ]. It is thought that the 2017 G2P[4] outbreak began in the NT and subsequently spread to rural and remote regions of WA adjacent to the border between these states [ 31 ]. A companion study described the weak protective effect of either Rotarix or RotaTeq vaccination in the setting of this outbreak [ 31 ].…”

“…It is thought that the 2017 G2P[4] outbreak began in the NT and subsequently spread to rural and remote regions of WA adjacent to the border between these states [ 31 ]. A companion study described the weak protective effect of either Rotarix or RotaTeq vaccination in the setting of this outbreak [ 31 ]. Sub-optimal vaccine-effectiveness, particularly in the second year of life, has been reported in other high-burden, low-resource settings [ 32 ].…”

Immunogenicity of a third scheduled dose of rotavirus vaccine in Australian Indigenous infants to improve protection against gastroenteritis: a phase IV, double-blind, randomised, placebo-controlled clinical trial

“…4 During two separate G2P [4] genotype rotavirus epidemics in the Northern Territory, rotavirus vaccine effectiveness was estimated (albeit imprecisely) to be as low as 20% (OR 0•81; 95% CI 0•32 -2•05 and OR 0•79; 95% CI 0•46 -1•34), with evidence of little or no protection after 12 months old. 5,6 Controlled trials in Africa suggest that administering three rather than two doses of Rotarix might provide more sustained protection against severe rotavirus gastroenteritis in those settings. These studies observed a trend towards higher clinical efficacy in the second year of life with three-dose vs two-dose schedules, albeit with wide and overlapping confidence intervals.…”

Rotaviruses and Rotavirus Vaccines

“…A range of factors have been implicated including higher rotavirus transmission rates, variations in gut microbiota, and host factors such as histo-blood group antigen (HBGA) and Lewis secretor antigens [ 15 ]. Middleton et al conducted a retrospective case–control study to evaluate the performance of Rotarix and RotaTeq during a G2P[4] rotavirus epidemic in rural and remote Australia [ 16 ]. The majority of affected children were Aboriginal and/or Torres Strait Islander; populations that experience a disproportionately high burden of rotavirus disease.…”

“…However, the overall protective effect of either Rotarix or RotaTeq in this setting was weak. The study highlights that even within a high-income country, certain populations will experience differing vaccine effectiveness, which suggests that tailored vaccine strategies and public health measures may be required to better protect these populations until the reasons for suboptimal vaccine effectiveness can be elucidated and addressed [ 16 ]. The strain associated with this outbreak was characterised by Donato et al and the demographics of the outbreak in Kimberley region of Western Australia was described [ 17 ].…”