Effectiveness of rotavirus vaccines in an Australian population: A case-control study

Rotavirus vaccine coverage, completion, and compliance: A systematic literature review

Rotavirus, a leading cause of severe acute gastroenteritis in children, is largely preventable through immunization with two internationally licensed oral rotavirus vaccines (RVVs) included in national programs across over 100 countries. These RVVs are administered in either two (Rotarix™; 2D-RV) or three (RotaTeq®; 3D-RV) doses. We aimed to assess the global coverage, completion, and compliance of 2D-RV and 3D-RV in various settings, and to identify factors influencing vaccine coverage. We conducted a systematic review of PubMed and Embase for articles published between 2006 and 2021. We included 74 publications across 31 countries. RVV coverage rates and the factors associated with coverage varied widely among countries based on income level, RVV used, and the year of vaccination. Due to market bias and insufficient studies, valid RVVs coverage comparisons couldn't be made. However, 2D-RV had better completion/compliance rates than 3D-RV in Italy, Mexico, and the US.

Genetic diversity of G9, G3, G8 and G1 rotavirus group A strains circulating among children with acute gastroenteritis in Vietnam from 2016 to 2021

Rotavirus group A (RVA) is the most common cause of severe childhood diarrhea worldwide. The introduction of rotavirus vaccination programs has contributed to a reduction in hospitalizations and mortality caused by RVA. From 2016 to 2021, we conducted surveillance to monitor RVA prevalence and genotype distribution in Nam Dinh and Thua Thien Hue (TT Hue) provinces where a pilot Rotavin-M1 vaccine (Vietnam) implementation took place from 2017 to 2020. Out of 6626 stool samples, RVA was detected in 2164 (32.6%) by ELISA. RT-PCR using type-specific primers were used to determine the G and P genotypes of RVA-positive specimens. Whole genome sequences of a subset of 52 specimens randomly selected from 2016 to 2021 were mapped using next-generation sequencing. From 2016 to 2021, the G9, G3 and G8 strains dominated, with detected frequencies of 39%, 23%, and 19%, respectively; of which, the most common genotypes identified were G9P[8], G3P[8] and G8P[8]. G1 strains re-emerged in Nam Dinh and TT Hue (29.5% and 11.9%, respectively) from 2020 to 2021. G3 prevalence decreased from 74% to 20% in TT Hue and from 21% to 13% in Nam Dinh province between 2017 and 2021. The G3 strains consisted of 52% human typical G3 (hG3) and 47% equine-like G3 (eG3). Full genome analysis showed substantial diversity among the circulating G3 strains with different backgrounds relating to equine and feline viruses. G9 prevalence decreased sharply from 2016 to 2021 in both provinces. G8 strains peaked during 2019-2020 in Nam Dinh and TT Hue provinces (68% and 46%, respectively). Most G8 and G9 strains had no genetic differences over the surveillance period with very high nucleotide similarities of 99.2-99.9% and 99.1-99.7%, respectively. The G1 strains were not derived from the RVA vaccine. Changes in the genotype distribution and substantial diversity among circulating strains were detected throughout the surveillance period and differed between the two provinces. Determining vaccine effectiveness against circulating strains over time will be important to ensure that observed changes are due to natural secular variation and not from vaccine pressure.

Cost-effectiveness analysis measuring the total costs against the health benefits of three different rotavirus vaccines for Mexico

Rotavirus (RV) infection causes acute rotavirus gastroenteritis (RVGE) in infants. Safe and effective RV vaccines are available, of which Mexico has included one in its national immunization program (NIP) since 2007. Health outcome gains, expressed in quality-adjusted life years (QALYs), and cost improvements are important additional factors for the selection of a NIP vaccine. These two factors were analyzed here for Mexico over one year implementing three RV vaccines: 2-dose Rotarix (HRV), versus 3-dose RotaTeq (HBRV), and 3-dose Rotasiil (BRV-PV), presented in a 1-dose or 2-dose vial). HRV would annually result in discounted QALY gains of 263 extra years compared with the other vaccines by averting an extra 24,022 homecare cases, 10779 medical visits, 392 hospitalizations, and 12 deaths. From a payer's perspective and compared with HRV, BRV-PV 2-dose vial and BRV-PV 1-dose vial would annually result in $13.5 million and $4.6 million net savings, respectively, while HBRV would result in $3.4 million extra costs. The societal perspective may also show savings compared with HRV for BRV-PV 2-dose vial of $4.9 million, while BRV-PV 1-dose vial and HBRV may show extra costs of $4.0 million and $12.1 million respectively. HRV and HBRV were both approved in Mexico, with HRV requiring less investment than HBRV with higher QALY gains and cost savings. The HRV vaccine produced those higher health gains due to its earlier protection and greater coverage achieved after its schedule completion with two doses only, providing full protection at four months of age instead of longer periods for the other vaccines.

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.

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

In May, 2017, an outbreak of rotavirus gastroenteritis was reported that predominantly impacted Aboriginal children ≤4 years of age in the Kimberley region of Western Australia. G2P[4] was identified as the dominant genotype circulating during this period and polyacrylamide gel electrophoresis revealed the majority of samples exhibited a conserved electropherotype. Full genome sequencing was performed on representative samples that exhibited the archetypal DS-1-like genome constellation: G2-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2 and phylogenetic analysis revealed all genes of the outbreak samples were closely related to contemporary Japanese G2P[4] samples. The outbreak samples consistently fell within conserved sub-clades comprised of Hungarian and Australian G2P[4] samples from 2010. The 2017 outbreak variant was not closely related to G2P[4] variants associated with prior outbreaks in Aboriginal communities in the Northern Territory. When compared to the G2 component of the RotaTeq vaccine, the outbreak variant exhibited mutations in known antigenic regions; however, these mutations are frequently observed in contemporary G2P[4] strains. Despite the level of vaccine coverage achieved in Australia, outbreaks continue to occur in vaccinated populations, which pose challenges to regional areas and remote communities. Continued surveillance and characterisation of emerging variants are imperative to ensure the ongoing success of the rotavirus vaccination program in Australia.

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.

Real-world effectiveness of rotavirus vaccines, 2006-19: a literature review and meta-analysis

BACKGROUND

Since licensure in 2006, rotavirus vaccines have been introduced in more than 100 countries. The efficacy of rotavirus vaccines is variable in settings with different child mortality levels. We did an updated review of the published literature to assess the real-world effectiveness of rotavirus vaccines in a range of settings.

METHODS

In this literature review and meta-analysis, we included observational, post-licensure studies of rotavirus vaccines, published from Jan 1, 2006, to Dec 31, 2019, in English, with laboratory-confirmed rotavirus as the endpoint. In addition to product-specific results for Rotarix (GlaxoSmithKline Biologicals, Rixensart, Belgium) or RotaTeq (Merck, West Point, PA, USA), we included Rotarix and RotaTeq mixed series, and non-product-specific vaccine effectiveness estimates from countries where Rotarix and RotaTeq are both available. Studies of other infant rotavirus vaccines were excluded because little or no post-licensure data were available. We fitted random-effects regression models to estimate vaccine effectiveness among children younger than 12 months and aged 12-23 months. On the basis of 2017 UNICEF mortality estimates for children younger than 5 years, countries were stratified as having low (lowest quartile), medium (second quartile), or high mortality (third and fourth quartiles).

FINDINGS

We identified and screened 1703 articles, of which 60 studies from 32 countries were included. 31 studies were from countries with low child mortality, eight were from medium-mortality countries, and 21 were from high-mortality countries. Rotarix vaccine effectiveness against laboratory-confirmed rotavirus among children younger than 12 months old was 86% (95% CI 81-90) in low-mortality countries, 77% (66-85) in medium-mortality countries, and 63% (54-70) in high-mortality countries. Rotarix vaccine effectiveness among children aged 12-23 months was 86% (81-90) in low-mortality countries, 54% (23-73) in medium-mortality countries, and 58% (38-72) in high-mortality countries. RotaTeq vaccine effectiveness among children younger than 12 months was 86% (76-92) in low-mortality countries and 66% (51-76) in high-mortality countries. RotaTeq vaccine effectiveness among children aged 12-23 months was 84% (79-89) in low-mortality countries. There was no substantial heterogeneity (I² range: 0-36%). Median vaccine effectiveness in low-mortality countries was similar for Rotarix (83%; IQR 78-91), RotaTeq (85%; 81-92), mixed series (86%; 70-91), and non-product-specific (89%; 75-91) vaccination.

INTERPRETATION

Rotavirus vaccines were effective in preventing rotavirus diarrhoea, with higher performance in countries with lower child mortality.

FUNDING

None.

Association between rotavirus vaccination and intussusception in Australian children: A record linkage study

BACKGROUND

Post-licensure surveillance studies have shown a small but increased risk of intussusception among infants in the days following rotavirus vaccination (RV).

OBJECTIVES

We assessed the temporal trends of intussusception-coded hospitalisations before and after the commencement of a universal rotavirus vaccination programme in Western Australia (WA) in 2007. We also assessed the perinatal factors and pathogens associated with these hospitalisations.

METHODS

Intussusception-coded hospitalisations occurring in a cohort of 367 476 WA-born children (2000-2012) aged <5 years were probabilistically linked to perinatal and pathology records. Age-specific incidence rates for overall and pathogen-specific intussusception-coded hospitalisations were calculated before (2000-2006) and after (2008-2012) RV introduction. Adjusted Cox proportional hazards models were used to assess perinatal risk factors for intussusception.

RESULTS

The overall rate of intussusception-coded hospitalisation was 26.4 per 100 000 child-years (95% confidence interval [CI] 24.0, 29.0) among children aged <5 years, with rates being 70% higher (95% CI 39, 107) in the RV period than in the pre-RV period. Compared with the pre-RV period, rates were higher among those aged 12-23 months (by 55%, 95% CI 5, 127) and 2-4 years (by 84%, 95% CI 20, 182) in the RV period. However, the risk of intussusception-coded hospitalisations associated with intussusception management-related procedure code(s) was similar among all age groups in both birth periods. Among infants aged <12 months, male sex, non-Aboriginal status, birth to multiparous mothers, and birth in RV era were independent risk factors associated with intussusception-coded hospitalisations. Adenovirus was strongly associated with intussusception (6.7 per 100 000 child-years, 95% CI 5.3, 9.3).

CONCLUSIONS

The risk of intussusception-coded hospitalisations was higher post-RV introduction, but not for intussusception-coded hospitalisations associated with procedure code(s). The increase was no higher in the vaccine-eligible age group than in older age groups, suggesting that the apparent increase is likely to be attributable to causes other than vaccination.

Fifteen years of experience with the oral live-attenuated human rotavirus vaccine: reflections on lessons learned

INTRODUCTION

Rotavirus (RV) disease remains a prominent cause of disease burden in children <5 years of age worldwide. However, implementation of RV vaccination has led to significant reductions in RV mortality, compared to the pre-vaccination era. This review presents 15 years of real-world experience with the oral live-attenuated human RV vaccine (HRV; Rotarix). HRV is currently introduced in ≥80 national immunization programs (NIPs), as 2 doses starting from 6 weeks of age.

AREAS COVERED

The clinical development of HRV and post-marketing experience indicating the impact of HRV vaccination on RV disease was reviewed.

EXPERT OPINION

In clinical trials, HRV displayed an acceptable safety profile and efficacy against RV-gastroenteritis, providing broad protection against heterotypic RV strains by reducing the consequences of severe RV disease in infants. Real-world evidence shows substantial, rapid reduction in the number of RV infections and associated hospitalizations following introduction of HRV in NIPs, regardless of economic setting. Indirect effects against RV disease are also observed, such as herd protection, decrease in nosocomial infections incidence, and a reduction of disease-related societal/healthcare costs. However, not all countries have implemented RV vaccination. Coverage remains suboptimal and should be improved to maximize the benefits of RV vaccination.