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

Histo-blood group antigen profile of Australian Aboriginal children and seropositivity following oral rotavirus vaccination

BACKGROUND

Histo-blood group antigens (HBGAs) may influence immune responses to rotavirus vaccination.

METHODS

HBGA phenotyping was determined by detection of antigens A, B, H and Lewis a and b in saliva using enzyme-linked immunosorbent assay. Secretor status was confirmed by lectin antigen assay if A, B and H antigens were negative or borderline (OD ± 0.1 of threshold of detection). PCR-RFLP analysis was used to identify the FUT2 'G428A' mutation in a subset. Rotavirus seropositivity was defined as serum anti-rotavirus IgA ≥ 20 AU/mL.

RESULTS

Of 156 children, 119 (76 %) were secretors, 129 (83 %) were Lewis antigen positive, and 105 (67 %) were rotavirus IgA seropositive. Eighty-seven of 119 (73 %) secretors were rotavirus seropositive, versus 4/9 (44 %) weak secretors and 13/27 (48 %) non-secretors.

CONCLUSIONS

Most Australian Aboriginal children were secretor and Lewis antigen positive. Non-secretor children were less likely to be seropositive to rotavirus antibodies following vaccination, but this phenotype was less common. HBGA status is unlikely to fully explain underperformance of rotavirus vaccines among Australian Aboriginal children.

Review of the health impact of the oral rotavirus vaccine program in children under 5 years in Australia: 2006 - 2021

Oral rotavirus vaccines were incorporated into the National Immunisation Program (NIP) for all Australian infants in July 2007. Initially each of the eight jurisdictions implemented Rotarix or RotaTeq rotavirus vaccine, however from July 2017 all states and territories have administered Rotarix only. This review evaluates the health impact of the oral rotavirus vaccine program for Australian children less than 5 years old over the first 15 years of the rotavirus vaccine program, observing long-term changes in rotavirus-related health care attendances, public health notifications, and vaccine effectiveness and safety data for both Rotarix and RotaTeq rotavirus vaccines. We searched Medline for studies published between January 2006 and May 2022 using the search terms 'rotavirus', 'rotavirus vaccine' and 'Australia'. Of 491 items identified, 76 items - 36 peer-reviewed articles and 40 reports - were included in the review. We found evidence that the introduction of the oral rotavirus vaccine program in Australia was associated with a prompt reduction in rotavirus-coded and all-cause gastroenteritis hospitalisations of vaccine-eligible children. In the context of less complete coverage, reduced vaccine timeliness and lower vaccine effectiveness, a less substantial and inconsistent reduction in severe rotavirus disease was observed among Aboriginal and Torres Strait Islander children, particularly those living in rural and remote northern Australia. Additional studies report no evidence for the emergence of non-vaccine serotypes and/ or replacement serotypes in Australia during the vaccine era. While the health impact for young children and consequent cost-savings of the oral rotavirus vaccine program have been high, it is important to find strategies to improve rotavirus vaccine impact for Aboriginal and Torres Strait Islander populations to ensure health benefits for all Australian children.

Impact of rotavirus vaccine implementation on Israeli children: a comparison between pre- and post-vaccination era

BACKGROUND

Worldwide rotavirus vaccination has resulted in a substantial decrease in rotavirus-induced severe gastroenteritis and related hospitalizations among children. Still, the characterization of patients warranting hospitalization needs to be further elucidated. The purpose of the study is to compare the clinical and laboratory features of children hospitalized with acute rotavirus infection before and after the introduction of routine vaccination.

METHODS

This is a retrospective observational study. Participants were pediatric patients who presented to the Bnai Zion Medical Center pediatric emergency department and were diagnosed with rotavirus acute gastroenteritis between 2017 and 2019.

RESULTS

During the pre-vaccination period (2007-2009), 114 infants and young children (median age: 14 months, range: 1-72 months; 59 male, 55 female) were hospitalized for rotavirus-induced acute gastroenteritis with a rate of 11.71 positive rotavirus tests per 1000 emergency room visits. In the post-vaccination period (2012-2019), 168 infants and young children (median age: 17 months, range: 0-84 months; 90 male, 78 female) were hospitalized with a rate of 4.18 positive rotavirus tests per 1000 emergency room visits. There were no statistical differences between the two groups in gender, breast-feeding rates and sibling(s). The proportion of cases with moderate-to-severe dehydration was higher in the post-vaccination children than in the pre-vaccination children.

CONCLUSIONS

Rates of rotavirus-attributed acute gastroenteritis hospitalizations declined from the pre- to the post-vaccination period. Higher rates of dehydration were found in the post-vaccination children. Ongoing surveillance is warranted to better understand the implications of the vaccine.

OUP accepted manuscript

Background

Rotarix (GlaxoSmithKline) oral rotavirus vaccine is licensed as 2 doses in the first 6 months of life. In settings with high child mortality rates, clinical protection conferred by 2 doses of Rotarix is reduced. We assessed vaccine immune response when an additional dose of Rotarix was given to Australian Aboriginal children 6 to <12 months old.

Methods

ORVAC is a 2-stage, double-blind, randomized, placebo-controlled trial. Australian Aboriginal children 6 to <12 months old who had received 1 or 2 prior doses of Rotarix rotavirus vaccine were randomized 1:1 to receive an additional dose of Rotarix or matched placebo. The primary immunological end point was seroresponse defined as an anti-rotavirus immunoglobulin A level ≥20 AU/mL, 28–56 days after the additional dose of Rotarix or placebo.

Results

Between March 2018 and August 2020, a total of 253 infants were enrolled. Of these, 178 infants (70%) had analyzable serological results after follow-up; 89 were randomized to receive Rotarix, and 89 to receive placebo. The proportion with seroresponse was 85% after Rotarix compared with 72% after placebo. There were no occurrences of intussusception or any serious adverse events.

Conclusions

An additional dose of Rotarix administered to Australian Aboriginal infants 6 to <12 months old increased the proportion with a vaccine seroresponse.

Clinical Trials Registration

NCT02941107.

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

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.

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

Objective

The purpose of this double-blind, randomised, placebo-controlled, adaptive design trial with frequent interim analyses is to determine if Australian Indigenous children, who receive an additional (third) dose of human rotavirus vaccine (Rotarix, GlaxoSmithKline) for children aged 6 to < 12 months, would improve protection against clinically significant all-cause gastroenteritis.

Participants

Up to 1000 Australian Aboriginal and Torres Strait Islander (hereafter Indigenous) infants aged 6 to < 12 months will be recruited from all regions of the Northern Territory.

Interventions

The intervention is the addition of a third scheduled dose of human monovalent rotavirus vaccine.

Co-primary and secondary outcome measures

ORVAC has two co-primary outcomes: (1) anti-rotavirus IgA seroconversion, defined as serum anti-rotavirus IgA ≥ 20 U/ml 28 to 55 days post Rotarix/placebo, and (2) time from randomisation to medical attendance for which the primary reason for presentation is acute gastroenteritis or acute diarrhoea illness before age 36 months. Secondary outcomes include (1) change in anti-rotavirus IgA log titre, (2) time from randomisation to hospitalisation with primary admission code presumed or confirmed acute diarrhoea illness before age 36 months, (3) time from randomisation to hospitalisation for which the admission is rotavirus confirmed diarrhoea illness before age 36 months and (4) time from randomisation to rotavirus infection (not necessarily requiring hospitalisation) meeting the jurisdictional definition before age 36 months.

Discussion

A detailed, prospective statistical analysis plan is presented for this Bayesian adaptive design. The plan was written by the trial statistician and details the study design, pre-specified adaptative elements, decision thresholds, statistical methods and the simulations used to evaluate the operating characteristics of the trial. As at August 2020, four interim analyses have been run, but no stopping rules have been triggered. Application of this SAP will minimise bias and supports transparent and reproducible research.

Trial registration

Clinicaltrials.gov NCT02941107. Registered on 21 October 2016

Original protocol for the study

10.1136/bmjopen-2019-032549