Rotavirus Disease and Genotype Diversity in Older Children and Adults in Australia.

BACKGROUND: Rotavirus is a major cause of gastroenteritis in children <5 years of age. The disease burden in older children, adults, and the elderly is underappreciated. This study describes rotavirus disease and genotypic diversity in the Australian population comprising children ≥5 years of age and adults. METHODS: Rotavirus positive fecal samples were collected from laboratories Australia-wide participating in the Australian Rotavirus Surveillance Program between 2010 and 2018. Rotavirus samples were genotyped using a heminested multiplex reverse-transcription polymerase chain reaction. Notification data from the National Notifiable Diseases Surveillance System were also analyzed. RESULTS: Rotavirus disease was highest in children aged 5-9 years and adults ≥85 years. G2P[4] was the dominant genotype in the population ≥5 years of age. Genotype distribution fluctuated annually and genotypic diversity varied among different age groups. Geographical differences in genotype distribution were observed based on the rotavirus vaccine administered to infants <1 year of age. CONCLUSIONS: This study revealed a substantial burden of rotavirus disease in the population ≥5 years of age, particularly in children 5-9 years and the elderly. This study highlights the continued need for rotavirus surveillance across the population, despite the implementation of efficacious vaccines.

Human Neonatal Rotavirus Vaccine (RV3-BB) to Target Rotavirus from Birth.

BACKGROUND: A strategy of administering a neonatal rotavirus vaccine at birth to target early prevention of rotavirus gastroenteritis may address some of the barriers to global implementation of a rotavirus vaccine. METHODS: We conducted a randomized, double-blind, placebo-controlled trial in Indonesia to evaluate the efficacy of an oral human neonatal rotavirus vaccine (RV3-BB) in preventing rotavirus gastroenteritis. Healthy newborns received three doses of RV3-BB, administered according to a neonatal schedule (0 to 5 days, 8 weeks, and 14 weeks of age) or an infant schedule (8 weeks, 14 weeks, and 18 weeks of age), or placebo. The primary analysis was conducted in the per-protocol population, which included only participants who received all four doses of vaccine or placebo within the visit windows, with secondary analyses performed in the intention-to-treat population, which included all participants who underwent randomization. RESULTS: Among the 1513 participants in the per-protocol population, severe rotavirus gastroenteritis occurred up to the age of 18 months in 5.6% of the participants in the placebo group (28 of 504 babies), in 1.4% in the neonatal-schedule vaccine group (7 of 498), and in 2.7% in the infant-schedule vaccine group (14 of 511). This resulted in a vaccine efficacy of 75% (95% confidence interval [CI], 44 to 91) in the neonatal-schedule group (P<0.001), 51% (95% CI, 7 to 76) in the infant-schedule group (P=0.03), and 63% (95% CI, 34 to 80) in the neonatal-schedule and infant-schedule groups combined (combined vaccine group) (P<0.001). Similar results were observed in the intention-to-treat analysis (1649 participants); the vaccine efficacy was 68% (95% CI, 35 to 86) in the neonatal-schedule group (P=0.001), 52% (95% CI, 11 to 76) in the infant-schedule group (P=0.02), and 60% (95% CI, 31 to 76) in the combined vaccine group (P<0.001). Vaccine response, as evidenced by serum immune response or shedding of RV3-BB in the stool, occurred in 78 of 83 participants (94%) in the neonatal-schedule group and in 83 of 84 participants (99%) in the infant-schedule group. The incidence of adverse events was similar across the groups. No episodes of intussusception occurred within the 21-day risk period after administration of any dose of vaccine or placebo, and one episode of intussusception occurred 114 days after the third dose of vaccine in the infant-schedule group. CONCLUSIONS: RV3-BB was efficacious in preventing severe rotavirus gastroenteritis when administered according to a neonatal or an infant schedule in Indonesia. (Funded by the Bill and Melinda Gates Foundation and others; Australian New Zealand Clinical Trials Registry number, ACTRN12612001282875 .).

The Impact of Rotavirus Vaccines on Genotype Diversity: A Comprehensive Analysis of 2 Decades of Australian Surveillance Data.

Background: Introduction of rotavirus vaccines into national immunization programs (NIPs) could result in strain selection due to vaccine-induced selective pressure. This study describes the distribution and diversity of rotavirus genotypes before and after rotavirus vaccine introduction into the Australian NIP. State-based vaccine selection facilitated a unique comparison of diversity in RotaTeq and Rotarix vaccine states. Methods: From 1995 to 2015, the Australian Rotavirus Surveillance Program conducted genotypic analysis on 13051 rotavirus-positive samples from children <5 years of age, hospitalized with acute gastroenteritis. Rotavirus G and P genotypes were determined using serological and heminested multiplex reverse-transcription polymerase chain reaction assays. Results: G1P[8] was the dominant genotype nationally in the prevaccine era (1995-2006). Following vaccine introduction (2007-2015), greater genotype diversity was observed with fluctuating genotype dominance. Genotype distribution varied based on the vaccine implemented, with G12P[8] dominant in states using RotaTeq, and equine-like G3P[8] and G2P[4] dominant in states and territories using Rotarix. Conclusions: The increased diversity and differences in genotype dominance observed in states using RotaTeq (G12P[8]), and in states and territories using Rotarix (equine-like G3P[8] and G2P[4]), suggest that these vaccines exert different immunological pressures that influence the diversity of rotavirus strains circulating in Australia.

Australian Rotavirus Surveillance Program annual report, 2012.

This report from the Australian Rotavirus Surveillance Program, together with collaborating laboratories Australia-wide, describes the rotavirus genotypes responsible for the hospitalisation of children with acute gastroenteritis during the period 1 January to 31 December 2012. During the survey period, 1,300 faecal samples were referred to the centre for rotavirus G and P genotype analysis, and of these 748 were confirmed as rotavirus positive. A total of 491 specimens were collected from children under 5 years of age, while 257 were from older children and adults. Genotype analysis revealed that G1P[8] was the dominant type in this reporting period, identified in 35% of strains nationally. Genotype G2P[4] was the second most common strain nationally, representing 28% of samples, followed by genotype G12P[8] (23%). This represents the first report where G12P[8] strains are a major cause of disease in this community. Fluctuations in genotype distribution were also observed based on the vaccine type in use. Genotype G2P[4] was more common in states and territories using Rotarix while G1P[8] was more common in states using RotaTeq. This survey of rotavirus strains circulating in 2012 highlights the continued fluctuations in rotavirus genotypes, with an annual change in dominant genotypes as well as emergence of a previously rare genotype, suggesting a dynamic wild-type population.

Rotavirus and the indigenous children of the Australian outback: monovalent vaccine effective in a high-burden setting.

Indigenous children living in arid Central Australia experience frequent outbreaks of rotavirus gastroenteritis. A widespread outbreak of G9 rotavirus infection occurred several months after introduction of the RIX4414 rotavirus vaccine. We performed a retrospective case-control study to determine vaccine efficacy during the outbreak. Two doses provided an estimated vaccine efficacy of 77.7% (95% confidence interval, 40.2%-91.7%) against hospitalization for gastroenteritis. Vaccine efficacy was 84.5% (95% confidence interval, 23.4%-96.9%) against confirmed cases of rotavirus infection. Vaccination was effective in this high-burden setting.

Safety and immunogenicity of RV3-BB human neonatal rotavirus vaccine administered at birth or in infancy: a randomised, double-blind, placebo-controlled trial.

BACKGROUND: Despite the success of rotavirus vaccines, suboptimal vaccine efficacy in regions with a high burden of disease continues to present a challenge to worldwide implementation. A birth dose strategy with a vaccine developed from an asymptomatic neonatal rotavirus strain has the potential to address this challenge and provide protection from severe rotavirus disease from birth. METHODS: This phase 2a randomised, double-blind, three-arm, placebo-controlled safety and immunogenicity trial was undertaken at a single centre in New Zealand between Jan 13, 2012, and April 17, 2014. Healthy, full-term (≥36 weeks gestation) babies, who weighed at least 2500 g, and were 0-5 days old at the time of randomisation were randomly assigned (1:1:1; computer-generated; telephone central allocation) according to a concealed block randomisation schedule to oral RV3-BB vaccine with the first dose given at 0-5 days after birth (neonatal schedule), to vaccine with the first dose given at about 8 weeks after birth (infant schedule), or to placebo. The primary endpoint was cumulative vaccine take (serum immune response or stool shedding of vaccine virus after any dose) after three doses. The immunogenicity analysis included all randomised participants with available outcome data. This trial is registered with the Australian New Zealand Clinical Trials Registry, ACTRN12611001212943. FINDINGS: 95 eligible participants were randomised, of whom 89 were included in the primary analysis. A cumulative vaccine take was detected in 27 (90%) of 30 participants in the neonatal schedule group after three doses of RV3-BB vaccine compared with four (13%) of 32 participants in the placebo group (difference in proportions 0·78, 95% CI 0·55-0·88; p<0·0001). 25 (93%) of 27 participants in the infant schedule group had a cumulative vaccine take after three doses compared with eight (25%) of 32 participants in the placebo group (difference in proportions 0·68, 0·44-0·81; p<0·0001). A serum IgA response was detected in 19 (63%) of 30 participants and 20 (74%) of 27 participants, and stool shedding of RV3-BB was detected in 21 (70%) of 30 participants and 21 (78%) of 27 participants in the neonatal and infant schedule groups, respectively. The frequency of solicited and unsolicited adverse events was similar across the treatment groups. RV3-BB vaccine was not associated with an increased frequency of fever or gastrointestinal symptoms compared with placebo. INTERPRETATION: RV3-BB vaccine was immunogenic and well tolerated when given as a three-dose neonatal or infant schedule. A birth dose strategy of RV3-BB vaccine has the potential to improve the effectiveness and implementation of rotavirus vaccines. FUNDING: Australian National Health and Medical Research Council, the New Zealand Health Research Council, and the Murdoch Childrens Research Institute.

Australian Rotavirus Surveillance Program annual report, 2010/11.

The Australian Rotavirus Surveillance Program together with collaborating laboratories Australia-wide conducts a laboratory based rotavirus surveillance program. This report describes the genotypes of rotavirus strains responsible for the hospitalisation of children with acute gastroenteritis during 1 July 2010 to 30 June 2011. This report represents the fourth year of surveillance following introduction of rotavirus vaccines into the National Immunisation Program. One thousand one hundred and twenty-seven faecal samples were referred to the centre for G and P genotype analysis using hemi-nested multiplex reverse transcription-polymerase chain reaction. Eight hundred and sixteen samples were confirmed as rotavirus positive. Of these, 551 were collected from children under 5 years of age, while 265 were from older children and adults. Genotype analysis revealed that a change in the dominant type occurred in this reporting period, such that genotype G2P[4] was the dominant type nationally, representing 51% of samples, followed by genotype G1P[8] (26.1%). Genotypes G3P[8] represented 11% of samples while G4P[8] re-emerged as an important genotype, and was identified in 6% of samples. Uncommon rotavirus G and P combinations continue to be identified, with G2P[8] and G9P[4] identified during this survey. Differences in genotype distribution based on vaccine usage continue to be evident in Australian states. This survey continues to highlight the fluctuations in rotavirus genotypes, with an annual change in dominant genotypes suggesting a more dynamic wild-type population.

Distribution of rotavirus genotypes after introduction of rotavirus vaccines, Rotarix® and RotaTeq®, into the National Immunization Program of Australia.

BACKGROUND: Rotavirus vaccines, RotaTeq and Rotarix, were introduced into the Australian National Immunization Program on July 1, 2007. The simultaneous introduction in different Australian states and territories provides a unique opportunity to compare the affect of each vaccine on the types of circulating rotavirus strains. This report describes the rotavirus genotypes responsible for the hospitalization of children during the first 2-year period after vaccine introduction. METHODS: A total of 764 rotavirus-associated diarrheal cases were collected from children presenting to hospital in 10 Australian centers. Rotavirus genotype was determined using reverse transcription polymerase chain reaction assays. RESULTS: G1P[8] was the dominant genotype nationally (52%), followed by G2P[4] (19.8%), G9P[8] (12.2%), and G3P[8] (11%). Differences in the prevalence rates of G2P[4] and G3P[8] were seen in the various states. G2P[4] strains were more prevalent in states using Rotarix, whereas G3P[8] strains were more prevalent in states using RotaTeq. CONCLUSIONS: Differences in rotavirus genotypes were observed across Australia, which suggest that different immune pressures are exerted by the different vaccines, but do not necessarily imply lack of protection by either vaccine. These differences may simply be related to the variation that can occur because of natural annual fluctuation in rotavirus strain prevalence.

Australian Rotavirus Surveillance Program: annual report, 2009/2010.

The Australian Rotavirus Surveillance Program together with 15 collaborating laboratories Australia-wide conducts a laboratory based rotavirus surveillance program. This report describes the genotypes of rotavirus strains responsible for the hospitalisation of children with acute gastroenteritis during the period 1 July 2009 to 30 June 2010, the 3rd year of surveillance following introduction of rotavirus vaccines into the National Immunisation Program. Seven hundred and seventy-eight faecal samples were referred to the centre for G and P genotype analysis using hemi-nested multiplex reverse transcription-polymerase chain reaction. Of the 422 confirmed as rotavirus positive, genotype G1P[8] was the dominant type nationally, representing 49.3%, followed by genotype G2P[4] (21.1%). Genotypes G3P[8], G4P[8] and G9P[8] each represented less than 3% of circulating strains nationally. The dominance of G1P[8] was in part associated with a large outbreak of severe gastroenteritis in the Northern Territory in 2010. The identification of uncommon rotavirus genotype combinations has increased since vaccine introduction, with G1P[4], G2P[8] and G9P[4] identified during this survey. Single strains of G1P[6] and G4P[6] were identified during this study period. This survey continues to highlight the fluctuations in rotavirus genotypes, and results from this survey suggest there is limited genotype selection based on vaccine usage. However, the large G1P[8] outbreak of gastroenteritis in the Northern Territory may have resulted from vaccine pressure on wild-type strains.

Australian Rotavirus Surveillance Program annual report, 2008/2009.

The Australian Rotavirus Surveillance Program together with collaborating laboratories Australia-wide, conducts a laboratory based rotavirus surveillance program. This report describes the genotypes of rotavirus strains responsible for the hospitalisation of children with acute gastroenteritis during the period 1 July 2008 to 30 June 2009, the second year of surveillance following introduction of rotavirus vaccine into the National Immunisation Program. Five hundred and ninety-two faecal samples from across Australia were examined for G and P genotype using hemi-nested multiplex reverse transcription-polymerase chain reaction assays. Of the 445 confirmed as rotavirus positive, genotype G2P[4] was the dominant type nationally, representing 50.3%, followed by genotype G1P[8] (22.5%). Genotypes G3P[8], G4P[8] and G9P[8] each represented less than 5% of circulating strains nationally. Uncommon rotavirus genotype combinations, including G1P[4] (n = 6), G4P[4] (n = 2) and single strains of G1P[6] and G3P[6] were identified during this study period. The national dominance of G2P[4] was associated with a large outbreak of severe gastroenteritis in Alice Springs in early 2009. This is the first report to describe G2P[4] as the dominant genotype nationally. Whether vaccine pressure has resulted in emergence of this genotype is not yet known.

Rotavirus strain surveillance--an Australian perspective of strains causing disease in hospitalised children from 1997 to 2007.

This study documents rotavirus strains causing severe disease in Australian children during the pre-vaccine era. During the period 1997-2007, rotavirus strains from national multi-centre hospital-based surveillance in Australia were analysed for G and P types. G1P[8] was the dominant genotype identified during the 11-year study, with intermittent peaks associated with genotypes G2P[4], G3P[8] and G9P[8]. The results provide baseline information of the G and P genotypes causing disease in Australian children, and highlight the unpredictable changes in genotype incidence that can occur on both a local and national level. To be optimally effective, rotavirus vaccines must prevent disease caused by all common rotavirus genotypes.

Australian Rotavirus Surveillance Program annual report, 2007/08.

The National Rotavirus Reference Centre together with collaborating laboratories Australia-wide conducts a laboratory based rotavirus surveillance program. This report describes the types of rotavirus strains responsible for the hospitalisation of children with acute gastroenteritis during the period 1 July 2007 to 30 June 2008, the first complete year of surveillance following introduction of rotavirus into the National Immunisation Program. Six hundred faecal samples from across Australia were examined using a combined approach of monoclonal antibody immunoassays and reverse transcription-polymerase chain reaction. Of the 419 confirmed as rotavirus positive, serotype G1 was the dominant serotype nationally, representing 52% of specimens, followed by serotype G2 (19.8%), serotype G9 (12.2%), and serotype G3 (11%). No serotype G4 strains were identified. All G1, G3 and G9 strains assayed for P genotype contained the P[8] genotype, while all G2 strains contained the P[4] genotype, except one G2 strain which possessed a P[8]. Uncommon rotavirus genotypes, G8 (n = 2) and P[9] (n = 2) were identified during this study period. There was no evidence of unexpected changes in serotype distribution during the first 12 months of rotavirus vaccine use in the National Immunisation Program.

Australian Rotavirus Surveillance Program: annual report, 2006-07.

The National Rotavirus Reference Centre, together with collaborating laboratories Australia-wide, conducts a laboratory based rotavirus surveillance program. This report describes the serotypes of rotavirus strains responsible for the hospitalisation of children with acute gastroenteritis during the period 1 July 2006 to 30 June 2007. One thousand and two faecal samples from across Australia were examined using a combined approach of monoclonal antibody immunoassays, reverse transcription-polymerase chain reaction and polyacrylamide gel analysis. Serotype G1 was the dominant serotype nationally, representing 36.7% of all strains, followed by serotype G9 (31.1%), and serotype G3 (23.3%). Serotype G2 represented less than 5% of strains, while no serotype G4 strains were identified. All G1, G3 and G9 strains assayed for P genotype contained the P[8] genotype, bar one G1 strain, which possessed a P[6]. Uncommon rotavirus genotypes, G8 (n = 1) and G12 (n = 2) were identified in children with acute gastroenteritis during this study period.

National Rotavirus Surveillance Program annual report, 2005-06.

The National Rotavirus Reference Centre together with collaborating laboratories Australia-wide has conducted rotavirus surveillance since June 1999. This report describes the serotypes of rotavirus strains responsible for the hospitalisation of children with acute gastroenteritis during the period 1 July 2005 to 30 June 2006. Eight hundred and forty-eight faecal samples from across Australia were examined using monoclonal antibody immunoassays, reverse transcription-polymerase chain reaction and polyacrylamide gel analysis. Serotype G1 was the dominant serotype nationally, representing 40.2 per cent of all strains, followed by serotype G4 (22.6%), serotype G9 (15.1%) and serotype G3 (14.7%). Genotype G12 strains were identified for the first time in Australia. As in previous years, there was substantial geographic variation in the prevalence of rotavirus serotypes.

Intussusception in the Northern Territory: the incidence is low in Aboriginal and Torres Strait Islander children.

AIM: To describe the epidemiology, immunisation status and management of children with intussusception in the Northern Territory (NT), 1993-2003. METHODS: Intussusception data were obtained from all NT hospitals using the International Classification of Diseases (ICD 9/10) codes for children under 18 years of age between 1993 and 2003. Medical records of these children were used to collect information on demographics, admission date, clinical symptoms, signs and management. Immunisation data were obtained from the NT immunisation register. The NT mortality database was reviewed for deaths from intussusception in children between 1993 and 2003. One death in an Aboriginal and Torres Strait Islander child was found in the NT mortality database. Medical records for this child were destroyed and so the case definition for intussusception used in this study was not fulfilled and the child was excluded. RESULTS: Intussusception proven by radiological or surgical means was identified in 23 children from hospital records. The incidence for children with intussusception in NT is 0.65/1000 live births. The incidence of intussusception was lower in Aboriginal and Torres Strait Islander children (0.16/1000 live births) than in non-Aboriginal and Torres Strait Islander children (0.92/1000 live births) (P < 0.01). CONCLUSION: The incidence of intussusception in the NT is similar to other developed countries but Aboriginal and Torres Strait Islander children have a very low incidence of intussusception. Intussusception is a rare event in the NT and will require a sensitive surveillance system to detect any potential increased risk of intussusception after the introduction of a new rotavirus vaccine.

National Rotavirus Surveillance Program annual report, 2004-05.

The National Rotavirus Reference Centre together with collaborating laboratories Australia-wide has conducted rotavirus surveillance since June 1999. This report describes the serotypes of rotavirus strains responsible for the hospitalisation of children with acute gastroenteritis during the period 1 July 2004 to 30 June 2005. Six hundred and twelve faecal samples from across Australia were examined using monoclonal antibody immunoassays, reverse transcription-polymerase chain reaction and polyacrylamide gel analysis. Serotype G1 was the dominant serotype nationally, representing 48.3 per cent of all strains, followed by serotype G3 (36.7%) and serotype G9 (6.9%). As in previous years, there was substantial geographic variation in the prevalence of rotavirus serotypes.

Validation of clinical case definition of acute intussusception in infants in Viet Nam and Australia.

OBJECTIVE: To test the sensitivity and specificity of a clinical case definition of acute intussusception in infants to assist health-care workers in settings where diagnostic facilities are not available. METHODS: Prospective studies were conducted at a major paediatric hospital in Viet Nam (the National Hospital of Pediatrics, Hanoi) from November 2002 to December 2003 and in Australia (the Royal Children's Hospital, Melbourne) from March 2002 to March 2004 using a clinical case definition of intussusception. Diagnosis of intussusception was confirmed by air enema or surgery and validated in a subset of participants by an independent clinician who was blinded to the participant's status. Sensitivity of the definition was evaluated in 584 infants aged<2 years with suspected intussusception (533 infants in Hanoi; 51 in Melbourne). Specificity was evaluated in 638 infants aged<2 years presenting with clinical features consistent with intussusception but for whom another diagnosis was established (234 infants in Hanoi; 404 in Melbourne). FINDINGS: In both locations the definition used was sensitive (96% sensitivity in Hanoi; 98% in Melbourne) and specific (95% specificity in Hanoi; 87% in Melbourne) for intussusception among infants with sufficient data to allow classification (449/533 in Hanoi; 50/51 in Melbourne). Reanalysis of patients with missing data suggests that modifying minor criteria would increase the applicability of the definition while maintaining good sensitivity (96-97%) and specificity (83-89%). CONCLUSION: The clinical case definition was sensitive and specific for the diagnosis of acute intussusception in infants in both a developing country and a developed country but minor modifications would enable it to be used more widely.

Report of the Australian rotavirus surveillance program 2002-03.

The National Rotavirus Reference Centre, together with collaborating laboratories Australia-wide, has conducted rotavirus surveillance since June 1999. This report describes the serotypes of rotavirus strains responsible for the hospitalisation of children with acute gastroenteritis during the period 1 July 2002 to 30 June 2003. We examined 573 faecal samples using monoclonal antibody immunoassays, reverse transcription-polymerase chain reaction, and polyacrylamide gel analysis. For the second consecutive year, serotype G9 strains were the most prevalent type nationally (74.7%) and were found in all seven contributing centres. Serotype G1 strains were the second most prevalent type (11.3%), identified in four of the centres. These findings have implications for vaccine development strategies which have targeted protection of disease due to serotypes G1-G4.