Epidemiological Profile and Burden of Rotavirus Diarrhea in Vietnam: 5 Years of Sentinel Hospital Surveillance, 1998–2003

Impact and effectiveness of Rotavin-M1 under conditions of routine use in two provinces in Vietnam, 2016-2021, an observational and case-control study

Background

Half of diarrhea hospitalizations in children aged <5 years in Vietnam are due to rotavirus. Following introduction of a locally developed and licensed oral rotavirus vaccine, Rotavin-M1, into the routine immunization program in two Vietnamese provinces, Nam Dinh and TT Hue, we describe changes in rotavirus positivity among children hospitalized for diarrhea and calculate vaccine effectiveness against moderate-to-severe rotavirus hospitalizations.

Methods

Active rotavirus surveillance among children <5 years began in December 2016 at sentinel hospitals in districts where rotavirus vaccine was introduced in December 2017. To estimate reductions in rotavirus detection, we calculated risk ratios comparing rotavirus positivity pre- and post-vaccine introduction. We used a test-negative case-control design to calculate vaccine effectiveness.

Findings

From December 2016 to May 2021, 7228 children <5 years hospitalized for diarrhea were enrolled. Following introduction, Rotavin-M1 coverage was 77% (1066/1377) in Nam Dinh and 42% (203/489) in TT Hue. In Nam Dinh, rotavirus positivity among children <5 years significantly declined by 40.6% (95% CI: 34.8%-45.8%) during the three-year post-vaccine introduction period. In TT Hue, no change in rotavirus positivity was observed. Among children aged 6-23 months, a 2-dose series of Rotavin-M1 was 57% (95% CI: 39%-70%) effective against moderate-to-severe rotavirus hospitalizations.

Interpretation

Higher vaccination coverage in Nam Dinh than TT Hue likely contributed to substantial declines in rotavirus positivity observed in Nam Dinh following rotavirus vaccine introduction. Robust vaccine effectiveness was observed through the second year of life. National rotavirus vaccine introduction with high coverage may have substantial impact on reducing rotavirus disease burden in Vietnam.

Funding

Bill and Melinda Gates Foundation.

Risk Factors Associated with Diarrheal Episodes in an Agricultural Community in Nam Dinh Province, Vietnam: A Prospective Cohort Study

In Vietnam, data on the risk factors for diarrhea at the community level remain sparse. This study aimed to provide an overview of diarrheal diseases in an agricultural community in Vietnam, targeting all age groups. Specifically, we investigated the incidence of diarrheal disease at the community level and described the potential risk factors associated with diarrheal diseases. In this prospective cohort study, a total of 1508 residents were enrolled during the 54-week study period in northern Vietnam. The observed diarrheal incidence per person-year was 0.51 episodes. For children aged <5 years, the incidence per person-year was 0.81 episodes. Unexpectedly, the frequency of diarrhea was significantly higher among participants who used tap water for drinking than among participants who used rainwater. Participants who used a flush toilet had less frequent diarrhea than those who used a pit latrine. The potential risk factors for diarrhea included the source of water used in daily life, drinking water, and type of toilet. However, the direct reason for the association between potential risk factors and diarrhea was not clear. The infection routes of diarrheal pathogens in the environment remain to be investigated at this study site.

The influence of human genetic variation on early transcriptional responses and protective immunity following immunization with Rotarix vaccine in infants in Ho Chi Minh City in Vietnam: A study protocol for an open single-arm interventional trial

Background: Rotavirus (RoV) remains the leading cause of acute gastroenteritis in infants and children aged under five years in both high- and low-middle-income countries (LMICs). In LMICs, RoV infections are associated with substantial mortality. Two RoV vaccines (Rotarix and Rotateq) are widely available for use in infants, both of which have been shown to be highly efficacious in Europe and North America. However, for unknown reasons, these RoV vaccines have markedly lower efficacy in LMICs. We hypothesize that poor RoV vaccine efficacy across in certain regions may be associated with genetic heritability or gene expression in the human host. Methods/design: We designed an open-label single-arm interventional trial with the Rotarix RoV vaccine to identify genetic and transcriptomic markers associated with generating a protective immune response against RoV. Overall, 1,000 infants will be recruited prior to Expanded Program on Immunization (EPI) vaccinations at two months of age and vaccinated with oral Rotarix vaccine at two and three months, after which the infants will be followed-up for diarrheal disease until 18 months of age. Blood sampling for genetics, transcriptomics, and immunological analysis will be conducted before each Rotarix vaccination, 2-3 days post-vaccination, and at each follow-up visit (i.e. 6, 12 and 18 months of age). Stool samples will be collected during each diarrheal episode to identify RoV infection. The primary outcome will be Rotarix vaccine failure events (i.e. symptomatic RoV infection despite vaccination), secondary outcomes will be antibody responses and genotypic characterization of the infection virus in Rotarix failure events. Discussion: This study will be the largest and best powered study of its kind to be conducted to date in infants, and will be critical for our understanding of RoV immunity, human genetics in the Vietnam population, and mechanisms determining RoV vaccine-mediated protection. Registration: ClinicalTrials.gov, ID: NCT03587389. Registered on 16 July 2018.

Prevalence and associated factors to rotavirus infection in children less than 5 years in Enugu State, Nigeria

Rotavirus is an important cause of morbidity and mortality in children 5 years and below. An epidemiological study was carried out to determine the prevalence of rotavirus in Enugu state and factors that contribute to the incidence in the state. Stool samples were collected from 179 children from different parts of the state. Rotavirus antigen was detected using enzyme immunoassay kit. A standardized structured questionnaire was used to obtain additional information from the parents/guardian of the children. Chi square was used to analyze the results and significance was determined at 0.05. The results showed 31.5% prevalence of rotavirus among children with acute gastroenteritis (AGE) and 25.7% prevalence in the general population. The prevalence was highest (60.9%) among children 0–12 months and decreased as the age increased. Rotavirus infection was significantly higher in bottle-fed children than in those feed exclusively breast milk. More viruses were detected in O (48.8%) and A (47.6%) blood group children than in children of other blood groups. More rotavirus caused AGE occurred in dry season compared to wet season, with highest incidence of both AGE and rotavirus infection occurring in January. Rotavirus diarrhoea was significantly associated with fever, vomiting and dehydration. The results of this study show that rotavirus continues to be an important cause of diarrhoea in children in this part of Nigeria and emphasize the need to factor in rotavirus and other viral agents in the diagnosis and treatment of diarrhoea in children 5 years and below.

Accounting for equity considerations in cost-effectiveness analysis: a systematic review of rotavirus vaccine in low- and middle-income countries

Background

Cost-effectiveness analysis (CEA) is frequently used as an input for guiding priority setting in health. However, CEA seldom incorporates information about trade-offs between total health gains and equity impacts of interventions. This study investigates to what extent equity considerations have been taken into account in CEA in low- and middle-income countries (LMICs), using rotavirus vaccination as a case study.

Methods

Specific equity-related indicators for vaccination were first mapped to the Guidance on Priority Setting in Health Care (GPS-Health) checklist criteria. Economic evaluations of rotavirus vaccine in LMICs identified via a systematic review of the literature were assessed to explore the extent to which equity was considered in the research objectives and analysis, and whether it was reflected in the evaluation results.

Results

The mapping process resulted in 18 unique indicators. Under the 'disease and intervention' criteria, severity of illness was incorporated in 75% of the articles, age distribution of the disease in 70%, and presence of comorbidities in 5%. For the 'social groups' criteria, relative coverage reflecting wealth-based coverage inequality was taken into account in 30% of the articles, geographic location in 27%, household income level in 8%, and sex at birth in 5%. For the criteria of 'protection against the financial and social effects of ill health', age weighting was incorporated in 43% of the articles, societal perspective in 58%, caregiver's loss of productivity in 45%, and financial risk protection in 5%. Overall, some articles incorporated the indicators in their model inputs (20%) while the majority (80%) presented results (costs, health outcomes, or incremental cost-effectiveness ratios) differentiated according to the indicators. Critically, less than a fifth (17%) of articles incorporating indicators did so due to an explicit study objective related to capturing equity considerations. Most indicators were increasingly incorporated over time, with a notable exception of age-weighting of DALYs.

Conclusion

Integrating equity criteria in CEA can help policy-makers better understand the distributional impact of health interventions. This study illustrates how equity considerations are currently being incorporated within CEA of rotavirus vaccination and highlights the components of equity that have been used in studies in LMICs. Areas for further improvement are identified.

Study protocol on establishment of sentinel sites network for contraceptive and abortion trends, needs and utilization of services in Zika virus affected countries

BACKGROUND

ZIKV(Zika Virus) during pregnancy can result in many adverse events such as fetal deaths or newborns with congenital abnormalities including microcephaly and other neural irregularities. Due to these harmful outcomes of pregnancy associated with the Zika virus, we can expect to see a change in the type and scale of demand for family planning and safe abortion services in areas affected by the Zika virus. The monitoring and reporting capacities of the local health clinics in these areas could benefit from the introduction of infrastructural improvements necessary to establish a sentinel site network. Through these sites, the WHO will collect data on the situation from local health professionals to get real time information from the population group and act accordingly to mitigate the consequences of the Zika virus outbreak in a localized and culturally appropriate way. The objectives are to establish a sentinel sites surveillance network for reporting on uptake and utilization of contraception and safe abortion care services; to strengthen monitoring, and data quality assurance in the selected sentinel surveillance sites; and finally to assess the contraception and safe abortion care service utilization trends in the affected sites on a regular basis.

METHODS

The proposal includes a set of objectives and actions that enable the creation of a set of criteria for the selection of the sentinel sites, as well the implementation of monitoring and reporting systems that will be used in data collection.

DISCUSSION

The data collected will be used to better understand the changing demand for family planning and safe abortion needs. This will ultimately be used to inform local health workers and policy makers as to how best to track the continued Zika virus outbreak and mitigate the consequences. The learning from establishment of surveillance sentinel sites will help to strengthen health systems at regional and subregional levels that are more adaptable and capable of providing reproductive healthcare services and of responding to future emergencies.

Prevalence and genetic diversity of rotavirus infection in children with acute gastroenteritis in a hospital setting, Nairobi Kenya in post vaccination era: a cross-sectional study

Introduction

Rotavirus is the leading cause of severe diarrhoea among infants and young children. Each year more than 611 000 children die from rotavirus gastroenteritis, and two million are hospitalized, worldwide. In Kenya, the impact of recent rotavirus vaccinations on morbidities has not been estimated. The study aimed at determining the prevalence and identity of rotavirus strains isolated from rotavirus-associated diarrhoea in vaccinated children presenting with acute gastroenteritis.

Methods

Two hundred and ninety eight specimen from children presented at Gertrude Childrens’ Hospital from January to June 2012 were tested by EIA (Enzyme-linked Immunosorbent Assay) for rotavirus antigens. Molecular characterization was conducted on rotavirus-positive specimens. Extracted viral RNA was separated by polyacrylamide gel electrophoresis (PAGE) and the specific rotavirus VP4 (P-types) and VP7 (G-types) determined.

Results

The prevalence rate of rotavirus was 31.5% (94/298). Of the rotavirus dsRNA, 57 (60.1%) gave visible RNA profiles, 38 (40.4%) assigned long electropherotypes while 19 (20.2%) were short electropherotypes. The strains among the vaccinated were G3P [4], G12P [6], G3P [6], G9P [4], G mixed G9/3P [4] and G1/3P [4]. Specifically, the G genotypes were G9/3 (5.3%), G9 (4.3%), G3 (4.3%), G12 (2.1%) and mixed G1/3 (1.1%). The P genotypes detected were P [4] (5.3%) and P [6] (5.3%).

Conclusion

The present study demonstrates diversity in circulating genotypes with emergence of genotypes G3, G9, G12 and mixed genotypes G9/3 and recommends that vaccines should be formulated with a broad range of strains to include G9 and G12.

Unbiased whole-genome deep sequencing of human and porcine stool samples reveals circulation of multiple groups of rotaviruses and a putative zoonotic infection

Coordinated and synchronous surveillance for zoonotic viruses in both human clinical cases and animal reservoirs provides an opportunity to identify interspecies virus movement. Rotavirus (RV) is an important cause of viral gastroenteritis in humans and animals. In this study, we document the RV diversity within co-located humans and animals sampled from the Mekong delta region of Vietnam using a primer-independent, agnostic, deep sequencing approach. A total of 296 stool samples (146 from diarrhoeal human patients and 150 from pigs living in the same geographical region) were directly sequenced, generating the genomic sequences of sixty human rotaviruses (all group A) and thirty-one porcine rotaviruses (thirteen group A, seven group B, six group C, and five group H). Phylogenetic analyses showed the co-circulation of multiple distinct RV group A (RVA) genotypes/strains, many of which were divergent from the strain components of licensed RVA vaccines, as well as considerable virus diversity in pigs including full genomes of rotaviruses in groups B, C, and H, none of which have been previously reported in Vietnam. Furthermore, the detection of an atypical RVA genotype constellation (G4-P[6]-I1-R1-C1-M1-A8-N1-T7-E1-H1) in a human patient and a pig from the same region provides some evidence for a zoonotic event.

Prevalence of rotavirus antibodies in breast milk and inhibitory effects to rotavirus vaccines

Rotavirus (RV) is the most common cause of childhood diarrhea worldwide, and several vaccines have been successfully developed to reduce the burden of disease. However, lower vaccine immunogenicity and efficacy in developing countries might be related to the virus-neutralizing activity of breast milk. We examined possible differences in breast milk antibody levels (total IgA antibody, RV-specific antibodies, and RV-neutralizing antibodies) between healthy mothers living in a rural area (n=145) and mothers living in an urban area (n=147) of Vietnam. Total IgA concentration was significantly higher in samples from mothers in the rural region than in samples from mothers in the urban region, whereas urban mothers had significantly higher RV-specific IgA antibody titers than did rural mothers. Neutralizing antibodies against RV strain G1P[8] were undetected in nearly one-half of the breast milk samples (45-48%), whereas the majority of the remaining samples had low antibody titers (2-16). Despite these low titers, the breast milk still reduced vaccine strain titers (2×10(6) plaque forming units/mL) up to 80% or more, even at a milk-to-virus ratio of 1:8. An increase in neutralizing anti-G1P[8] antibody titers (P<0.05) in rural infants over time suggests a continuous exposure to circulating RV. These results contribute to the understanding of the potential interference of breast milk with RV vaccine efficacy and immunogenicity in Vietnamese infants.

Family impact of Rotavirus Gastroenteritis in Taiwan and Vietnam: an Ethnographic Study

Background

Prior to the introduction of rotavirus vaccines, rotavirus was the leading cause of severe gastroenteritis in infants and young children, and it continues to be the leading cause in countries without vaccination programs. Rotavirus gastroenteritis results in substantial economic burden and has a pronounced effect on the family of those who are ill. Both in Taiwan and in Vietnam, rotavirus illness is viewed as a priority disease. This study assessed, in Taiwan and Vietnam, the impact of rotavirus gastroenteritis on the family among a group of parents whose children had recently been hospitalized for this illness.

Methods

In the first half of 2013, parents of children who had been hospitalized due to rotavirus infection were recruited from hospitals in Taiwan (n = 12) and Vietnam (n = 22), and participated in focus group sessions or in-depth ethnographic interviews.

Results

In both countries, the results point to a substantial burden on the parents concerning emotions and logistics of daily tasks, and to considerable disruptions of the family routine. Taiwanese parents reported satisfaction with the health care system, a great deal of effort to suppress emotions, a fair amount of knowledge about rotavirus, and little extra costs related to the illness. On the other hand, parents in Vietnam expressed concern about the emotional well-being of and the health care treatments for their children, were less knowledgeable regarding rotavirus infection, and experienced a substantial financial burden due to indirect costs that were related to accessing treatment.

Conclusions

Families in Taiwan and Vietnam suffer from a considerable economic and emotional burden related to rotavirus gastroenteritis. One way to substantially reduce this burden is to provide universal and affordable rotavirus vaccination to susceptible children, especially since cost-effectiveness studies have demonstrated that universal vaccination would be safe and efficacious against severe rotavirus gastroenteritis in these countries.

Association between norovirus and rotavirus infection and histo-blood group antigen types in Vietnamese children

Norovirus and rotavirus are the two most important causes of acute gastroenteritis in children worldwide. Both norovirus and rotavirus recognize human histo-blood group antigens (HBGAs), and multiple binding patterns for HBGAs have been reported. To explore the role of HBGAs in host susceptibility to norovirus and rotavirus, we conducted a cross-sectional study in children hospitalized with diarrhea in northern Vietnam from September 2010 through September 2012. Of 260 children with paired stool and saliva samples, 158 (61%) were classified as HBGA secretors (Lea-b+), 31 (12%) were nonsecretors (Lea+b-), and 71 (27%) were partial secretors (Lea+b+). Norovirus was detected in 50 patients (19%), with viral genotypes GII.3 (n=28) and GII.4 (n=22) being the most common. All children infected with norovirus strains of genotype GII.4 were either HBGA secretors or partial secretors. Of the 28 GII.3 cases, 12 involved HBGA secretors, 11 partial secretors, and 5 nonsecretors. A total of 85 children tested positive for rotavirus, 74 of whom were infected with genotype P[8], 5 with P[4], and 6 with P[6]; all were HBGA secretors or partial secretors. This is the first epidemiological study demonstrating in a population that HBGA phenotype is a key susceptibility factor for both norovirus and rotavirus infections in children.

Incidence and Epidemiology of Intussusception among Infants in Ho Chi Minh City, Vietnam

OBJECTIVE

To evaluate rates of intussusception hospitalization among infants in Vietnam before the introduction of rotavirus vaccine.

STUDY DESIGN

Between 2009 and 2011, we identified intussusception hospitalizations among infants using the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Clinical Modification code K56.1 at 2 large pediatric hospitals in Ho Chi Minh City, Vietnam that treat most of the intussusception cases in the city. We reviewed all medical records to confirm a Brighton level 1 case definition for intussusception.

RESULTS

We identified a total of 869 intussusception cases in Ho Chi Minh City during the 3-year study period, for an annual rate of 296 per 100,000 infants. The mean age of intussusception was ∼ 37 weeks (8.6 months), with <2% of the cases occurring before age 15 weeks. Cases of intussusception were observed year-round in these hospitals with no evident seasonal pattern. Ultrasonography was used to diagnose most cases (97%), and reduction was performed by air enema in >95% of the cases, with only 1% of cases at 1 hospital and 5% at the other hospital requiring surgical intervention. Ultrasound diagnosis was confirmed by an independent radiologist in 94% of a randomly selected group of intussusception cases at 1 of the 2 hospitals. No mortality was reported.

CONCLUSION

Vietnam has a substantially higher rate of intussusception in children aged >15 weeks compared with most other regions of the world. Most of our cases were diagnosed by ultrasound, and only a small proportion required surgical intervention with no fatalities, suggesting that the higher rates may be related in part to better and earlier detection of intussusception.

A High Incidence of Intussusception Revealed by a Retrospective Hospital-Based Study in Nha Trang, Vietnam between 2009 and 2011

Rotavirus is a leading cause of severe diarrhea among children worldwide. Thus, the World Health Organization recommended including rotavirus vaccines in national immunization programs. One concern about rotavirus vaccine, however, is a possible association with intussusception. Thus, it is crucial to know the baseline incidence of intussusception in the first year of life. A study conducted in Hanoi, Vietnam showed that the incidence of intussusception was the highest in the world. This retrospective cross-sectional study was undertaken to determine the incidence of intussusception among children <5 years of age in Nha Trang, Vietnam. Hospital charts between 2009 and 2011 were reviewed in Khanh Hoa Provincial General Hospital where virtually all cases of intussusception occurring in the city were assumed to have been encountered. The incidence of intussusception among children <1 year of age was 296 per 100,000 person-years (95% confidence interval [CI]: 225–382), and that among children <5 years of age was 196 per 100,000 person-years (95% CI: 169–226), confirming the high incidence of intussusception in Vietnam. Nevertheless, there was no intussusception in the first three months of life. We therefore recommend that the first dose of any rotavirus vaccine be administered to infants between 6 and 12 weeks of age.

Global seasonality of rotavirus disease

BACKGROUND

A substantial number of surveillance studies have documented rotavirus prevalence among children admitted for dehydrating diarrhea. We sought to establish global seasonal patterns of rotavirus disease before the introduction of widespread vaccination.

METHODS

We reviewed studies of rotavirus detection in children with diarrhea published since 1995. We assessed potential relationships between seasonal prevalence and locality by plotting the average monthly proportion of diarrhea cases positive for rotavirus according to geography, country development and latitude. We used linear regression to identify variables that were potentially associated with the seasonal intensity of rotavirus.

RESULTS

Among a total of 99 studies representing all 6 geographic regions of the world, patterns of year-round disease were more evident in low- and low-middle income countries compared with upper-middle and high-income countries where disease was more likely to be seasonal. The level of country development was a stronger predictor of strength of seasonality (P = 0.001) than geographic location or climate. However, the observation of distinctly different seasonal patterns of rotavirus disease in some countries with similar geographic location, climate and level of development indicate that a single unifying explanation for variation in seasonality of rotavirus disease is unlikely.

CONCLUSION

While no unifying explanation emerged for varying rotavirus seasonality globally, the country income level was somewhat more predictive of the likelihood of having seasonal disease than other factors. Future evaluation of the effect of rotavirus vaccination on seasonal patterns of disease in different settings may help understand factors that drive the global seasonality of rotavirus disease.

A dose-escalation safety and immunogenicity study of a new live attenuated human rotavirus vaccine (Rotavin-M1) in Vietnamese children

We tested a candidate live, oral, rotavirus vaccine (Rotavin-M1™) derived from an attenuated G1P [8] strain (KH0118-2003) isolated from a child in Vietnam. The vaccine was tested first for safety in 29 healthy adults. When deemed safe, it was further tested for safety and immunogenicity in 160 infants (4 groups) aged 6-12 weeks in a dose and schedule ranging study. The vaccine was administered in low titer (10(6.0)FFU/dose) on a 2-dose schedule given 2 months apart (Group 2L) and on a 3-dose schedule given 1 month apart (Group 3L) and in high titer (10(6.3)FFU/dose) in 2 doses 2 months apart (Group 2H) and in 3 doses 1 month apart (Group 3H). For comparison, 40 children (group Rotarix™) were given 2 doses of the lyophilized Rotarix™ vaccine (10(6.5)CCID(50)/dose) 1 month apart. All infants were followed for 30 days after each dose for clinical adverse events including diarrhea, vomiting, fever, abdominal pain, irritability and intussusception. Immunogenicity was assessed by IgA seroconversion and viral shedding was monitored for 7 days after administration of each dose. Two doses of Rotavin-M1 (10(6.3)FFU/dose) were well tolerated in adults. Among infants (average 8 weeks of age at enrollment), administration of Rotavin-M1 was safe and did not lead to an increased rate of fever, diarrhea, vomiting or irritability compared to Rotarix™, indicating that the candidate vaccine virus had been fully attenuated by serial passages. No elevation of levels of serum transaminase, blood urea, or blood cell counts were observed. The highest rotavirus IgA seroconversion rate (73%, 95%CI (58-88%)) was achieved in group 2H (2 doses--10(6.3)FFU/dose, 2 months apart). The 2 dose schedules performed slightly better than the 3 dose schedules and the higher titer doses performed slightly better than the lower titer doses. These rates of seroconversion were similar to that of the Rotarix™ group (58%, 95%CI (42-73%)). However more infants who received Rotarix™ (65%) shed virus in their stool after the first dose than those who received Rotavin-M1 (44-48%) (p<0.05) and the percent shedding decreased after subsequent doses of either vaccine. Rotavin-M1 vaccine is safe and immunogenic in Vietnamese infants. A trial in progress will assess the safety, immunogenicity and efficacy of Rotavin-M1 (2 doses at 10(6.3)FFU/dose) in a larger number of infants. The trial registration numbers are NCT01375907 and NCT01377571.

Animal livestock and the risk of hospitalized diarrhoea in children under 5 years in Vietnam

OBJECTIVE

To investigate the association between environmental exposure to livestock and incidence of diarrhoea among Vietnamese children.

METHODS

A population-based cohort of 353,525 individuals, living in 75,828 households in Khanh Hoa Province, Vietnam, with baseline data covering geo-referenced information on demography, socio-economic status and household animals was investigated. Geographic information system was applied to calculate the density of livestock. The data were linked to hospitalized diarrhoea cases of children under 5 years recorded at two hospitals treating patients from the area as inpatients in the study area.

RESULTS

Overall, 3116 children with diarrhoea were hospitalized during the study period. The incidence of diarrhoea hospitalization was 60.8/1000 child-years. Male gender, age <2 years, higher number of household members and lack of tap water were significantly associated with an increased risk of diarrhoea. There was no evidence that ownership of livestock increased the risk of diarrhoea. In spatial analysis, we found no evidence that a high density of any animals was associated with an increased risk of diarrhoea.

CONCLUSIONS

Exposure to animals near or in households does not seem to constitute a major risk for diarrhoea in children under the age of 5 in Vietnam. Public health interventions to reduce childhood diarrhoea burden should focus on well-recognized causes such as sanitation, personal hygiene, access to adequate clean water supply and vaccination.

Genetic variation in the VP7 gene of rotavirus G1P[8] strains isolated in Vietnam, 1998-2009

Group A rotavirus genotype G1P[8] is the most common strain affecting humans around the world over the past few decades. In this study, we examined genetic variation in the VP7 gene of rotavirus G1P[8] strains, detected in children of four major cities of Vietnam during three different rotavirus seasons: 1998-1999, 2007-2008 and 2008-2009 in order to assess the evolution of the virus over 11 years. Fecal samples (n=73) from children hospitalized for gastroenteritis caused by G1P[8] rotavirus were analyzed by DNA sequencing of gene 9 encoding the VP7 capsid protein. Phylogenetic analyses indicated that VP7 gene of the G1 strains from 1999 contained a lineage I, while rotaviruses from 2009 clustered in lineage II. Both of these lineages were found co-circulating in 2007-2008 season. While different sublineages of lineage I and II co-circulated in the 1998-1999 and 2007-2008 seasons, almost all strains in 2009 belonged to sub-lineage II-C. In the analysis using selected 10 strains, the VP4 genes of these 2 VP7-G1 lineages were all grouped in F45-like cluster. Deduced amino acid analyses indicated that there were thirteen amino acid substitutions between strains of two lineages. Of those, two were found in antigenic regions A and C, implying possible antigenic differences between these two lineages. The G1P[8] strains in Vietnam are very genetically diverse and dynamic, implying the frequent monitoring on evolution of rotavirus will be important to assess efficacy of rotavirus vaccine in Vietnam.

Burden of rotavirus gastroenteritis and distribution of rotavirus strains in Asia: a systematic review

BACKGROUND

Rotavirus is the leading cause of severe diarrhea in children worldwide. We systematically reviewed the burden of rotavirus gastroenteritis (RVGE) and distribution of rotavirus strains in Asia.

METHODS

We searched MEDLINE, EMBASE and the World Health Organization (WHO) website for the term "rotavirus" and the name of each country. We included studies that were conducted in children between 2000 and 2011 and that examined the epidemiology, health and/or economic burden of RVGE, and G and P-type distribution in Eastern, South East, Southern and Central Asia. Random effects models were used to pool the proportions of RVGE. We also estimated child mortality due to RVGE using the updated WHO and United Nations Children's Fund's mortality estimates in 2008.

RESULTS

The search identified 113 eligible articles. The incidence rates of rotavirus-related hospitalizations in children under 5 years of age ranged from 2.1 to 20.0 cases per 1000 children per year with the highest rates reported in Bangladesh, South Korea, Taiwan, Thailand, and Vietnam. Rotavirus accounted for 37.5% of year-round hospitalized gastroenteritis cases, with higher proportions reported in South East Asia. Rotavirus was associated with approximately 145,000 deaths every year in Asia, with the greatest numbers occurring in India, Pakistan, and Indonesia. The highest annual societal costs of treating RVGE were reported in China (US$365 million), followed by Japan (US$254 million) and India (US$41-72 million). A diversity of rotavirus G and P-types was observed across Asia and the distribution of strains differed by country and year. The most common strains were G1P[8] (23.6%), G2P[4] (11.8%), G3P[8] (18.9%), and G9P[8] (7.4%).

CONCLUSIONS

Rotavirus is associated with substantial hospitalizations and deaths among children and causes large healthcare expenditures throughout Asia. Safe and effective rotavirus vaccines could substantially reduce the burden of disease.

The emergence of rotavirus G12 and the prevalence of enteric viruses in hospitalized pediatric diarrheal patients in southern Vietnam

Diarrhea is a major cause of childhood morbidity and mortality in developing countries, and the majority of infections are of viral etiology. We aimed to compare the etiological prevalence of the major enteric viruses in an urban and a rural setting in southern Vietnam. We simultaneously screened fecal specimens from 362 children in Ho Chi Minh City and Dong Thap province that were hospitalized with acute diarrhea over a 1-month-long period for four viral gastrointestinal pathogens. Rotavirus was the most common pathogen identified, but there was a differential prevalence of rotavirus and norovirus between the urban and rural locations. Furthermore, rotavirus genotyping and phylogenetic analysis again differentiated the genotypes by the sampling location. Our data show a disproportional distribution of enteric viral pathogens in urban and rural locations, and we provide evidence of continual importation of new rotavirus strains into southern Vietnam and report the emergence of rotavirus genotype G12.

Measuring the Impact of Rotavirus Acute Gastroenteritis Episodes (MIRAGE): A prospective community-based study

BACKGROUND

Current assessments of the burden of rotavirus (RV)-related gastroenteritis are needed to evaluate the potential benefits of RV immunization interventions. The objective of the present study was to characterize the burden of RV gastroenteritis among children presenting in outpatient settings with gastroenteritis.

METHODS

Between January and June 2005, 395 children younger than three years of age presenting with gastroenteritis symptoms (at least three watery or looser-than-normal stools, or forceful vomiting within the previous 24 h period) were recruited from 59 Canadian clinics and followed for two weeks. Stool specimens were tested for the RV antigen. Gastroenteritis-related symptoms, health care utilization, parental work loss and other cases of gastroenteritis in the household were assessed by questionnaires and daily symptom cards that were completed by caregivers.

RESULTS

Of 336 conclusive test results, 55.4% were RV positive (RV+). In addition to diarrhea, 67.2% and 89.3% of RV+ children experienced fever or vomiting, respectively. Compared with RV-negative (RV-) children, RV+ children were more likely to experience the three symptoms concurrently (57.0% versus 26.7%; P<0.001), to be hospitalized (12.9% versus 3.9%; P=0.008) and to induce parental work loss (53.8% versus 37.3%; P=0.003). The median duration of gastroenteritis was eight days for RV+ children (nine days for RV- children). Additional cases of gastroenteritis were present in 46.8% of households in the RV+ group (51.3% of households in the RV- group).

CONCLUSIONS

RV gastroenteritis cases were more severe than other gastroenteritis cases, were hospitalized more often and were associated with considerably more work loss.

Maternal antibodies to rotavirus: could they interfere with live rotavirus vaccines in developing countries?

INTRODUCTION

Past experience with live oral vaccines including licensed rotavirus vaccines demonstrates a trend towards reduced vaccine efficacy in developing countries compared with developed countries. The reasons behind this disparity are not well understood. Transplacental transfer of maternal antibodies and breast milk ingestion may attenuate vaccine responses in infants in developing countries where rotavirus infections are endemic, and maternal antibody levels are high. We examined the prevalence and level of rotavirus antibody in maternal and cord serum, colostrum and breast milk in a developing country setting.

METHODS

100 mother-infant pairs were prospectively recruited from December 2008 to February 2009 at Dr. Sardjito Hospital, Yogyakarta, Indonesia. Maternal and cord sera were collected during delivery. Colostrum and transitional breast milk were collected between day 0-3 and day 7-10 postpartum respectively. Rotavirus-specific IgA and IgG were estimated for all specimens and virus neutralization assays were conducted on a subset of milk specimens.

RESULTS

All maternal and cord serum samples were positive for rotavirus-specific IgG antibodies with a strong correlation between levels of rotavirus-specific IgG in mothers and levels transferred to infants in cord blood (r=0.86; p=0.001). 78% of colostrum and 67% of transitional breast milk specimens were positive for rotavirus-specific IgA. There was a median 4-fold decrease in rotavirus-specific IgA from colostrum to transitional breast milk. Neutralizing antibodies were present in 56% of colostrum specimens assayed (19/34) and in 41% of transitional milk specimens assayed (14/34).

CONCLUSIONS

Maternal serum and breast milk antibodies to rotavirus are highly prevalent in a developing country setting. Evaluation of the impact of maternal anti-rotavirus serum and breast milk antibody upon vaccine immunogenicity would help to inform rotavirus vaccination strategies, especially in developing settings.

Inhibitory effect of breast milk on infectivity of live oral rotavirus vaccines

BACKGROUND

Live oral rotavirus vaccines have been less immunogenic and efficacious among children in poor developing countries compared with middle income and industrialized countries for reasons that are not yet completely understood. We assessed whether the neutralizing activity of breast milk could lower the titer of vaccine virus and explain this difference in vitro.

METHODS

Breast milk samples were collected from mothers who were breast-feeding infants 4 to 29 weeks of age (ie, vaccine eligible age) in India (N = 40), Vietnam (N = 77), South Korea (N = 34), and the United States (N = 51). We examined breast milk for rotavirus-specific IgA and neutralizing activity against 3 rotavirus vaccine strains-RV1, RV5 G1, and 116E using enzyme immunoassays. The inhibitory effect of breast milk on RV1 was further examined by a plaque reduction assay.

FINDINGS

Breast milk from Indian women had the highest IgA and neutralizing titers against all 3 vaccine strains, while lower but comparable median IgA and neutralizing titers were detected in breast milk from Korean and Vietnamese women, and the lowest titers were seen in American women. Neutralizing activity was greatest against the 2 vaccine strains of human origin, RV1 and 116E. This neutralizing activity in one half of the breast milk specimens from Indian women could reduce the effective titer of RV1 by ∼2 logs, of 116E by 1.5 logs, and RV5 G1 strain by ∼1 log more than that of breast milk from American women.

INTERPRETATION

The lower immunogenicity and efficacy of rotavirus vaccines in poor developing countries could be explained, in part, by higher titers of IgA and neutralizing activity in breast milk consumed by their infants at the time of immunization that could effectively reduce the potency of the vaccine. Strategies to overcome this negative effect, such as delaying breast-feeding at the time of immunization, should be evaluated.

Sequence analysis of the VP7 gene of human rotaviruses G2 and G4 isolated in Japan, China, Thailand, and Vietnam during 2001-2003

Sequence and phylogenetic analyses of the rotavirus VP7 gene were performed on 52 human G2 and G4 strains isolated in Japan, China, Thailand, and Vietnam during 2001-2003. All genotype G2 strains included in the study clustered into lineage II of the phylogenetic tree, together with the majority of global G2 strains detected since 1995. The amino acid substitution at position 96 from aspartic acid to asparagine was noted among the emerging or re-emerging G2 rotavirus strains in Japan, Thailand, and Vietnam during 2002-2003. Genotype G4 strains detected in Vietnam grouped into lineage Ia of the phylogenetic tree, whereas Japanese G4 strains clustered in lineage Ic which included emerging G4 strains from Argentina, Italy, Paraguay, and Uruguay. It is noteworthy that an insertion of asparagine was found at position 76 in all the Japanese strains and that its presence might be involved in the emergence of G4 rotavirus in Japan during 2002-2003.

Development and characterization of candidate rotavirus vaccine strains derived from children with diarrhoea in Vietnam

In Vietnam, rotavirus infection accounts for more than one-half of all hospitalizations for diarrhoea among children less than 5 years of age. While new vaccines to prevent rotavirus diarrhoea have been developed and introduced into some countries by multinational manufacturers, the ability for developing countries such as Vietnam to introduce several new and important vaccines into the routine infant immunization schedule may be challenging. In order to be partially self-sufficient in vaccine production, Vietnam has pursued the development of several rotavirus strains as candidate vaccines using isolates obtained from Vietnamese children with diarrhoea. This paper describes the origin, isolation and characterization of 3 human rotavirus strains being considered for further vaccine development in Vietnam. The goal is to prepare a monovalent G1P [8] rotavirus vaccine using one of these strains obtained in Vietnam and naturally attenuated by multiple passages in cell culture. While this is an ambitious project that will require several years' work, we are using the lessons learned to improve the overall quality of vaccine production including the use of Vero cell techniques for the manufacture of other vaccines in Vietnam.

Cost-effectiveness of Rotavirus vaccination in Vietnam

BACKGROUND

Rotavirus is the most common cause of severe diarrhea leading to hospitalization or disease-specific death among young children. New rotavirus vaccines have recently been approved. Some previous studies have provided broad qualitative insights into the health and economic consequences of introducing the vaccines into low-income countries, representing several features of rotavirus infection, such as varying degrees of severity and age-dependency of clinical manifestation, in their model-based analyses. We extend this work to reflect additional features of rotavirus (e.g., the possibility of reinfection and varying degrees of partial immunity conferred by natural infection), and assess the influence of the features on the cost-effectiveness of rotavirus vaccination.

METHODS

We developed a Markov model that reflects key features of rotavirus infection, using the most recent data available. We applied the model to the 2004 Vietnamese birth cohort and re-evaluated the cost-effectiveness (2004 US dollars per disability-adjusted life year [DALY]) of rotavirus vaccination (Rotarix) compared to no vaccination, from both societal and health care system perspectives. We conducted univariate sensitivity analyses and also performed a probabilistic sensitivity analysis, based on Monte Carlo simulations drawing parameter values from the distributions assigned to key uncertain parameters.

RESULTS

Rotavirus vaccination would not completely protect young children against rotavirus infection due to the partial nature of vaccine immunity, but would effectively reduce severe cases of rotavirus gastroenteritis (outpatient visits, hospitalizations, or deaths) by about 67% over the first 5 years of life. Under base-case assumptions (94% coverage and $5 per dose), the incremental cost per DALY averted from vaccination compared to no vaccination would be $540 from the societal perspective and $550 from the health care system perspective.

CONCLUSION

Introducing rotavirus vaccines would be a cost-effective public health intervention in Vietnam. However, given the uncertainty about vaccine efficacy and potential changes in rotavirus epidemiology in local settings, further clinical research and re-evaluation of rotavirus vaccination programs may be necessary as new information emerges.

Rotavirus G5P[6] in child with diarrhea, Vietnam

We detected rotavirus G5P[6] with a long RNA pattern in a Vietnamese child with diarrhea. Viral outer capsid protein VP7 and VP4 genes suggest that it likely originated from porcine rotavirus either by genetic reassortment or as whole virions. To our knowledge, this is the first report of human rotavirus G5 in Asia.

Implementing rotavirus vaccination in Asia

At the 2006 meeting of the Asian Pacific Pediatric Association (APPA), the Asia Pacific regional rotavirus community and international experts strongly recommended that rotavirus vaccines be used in National Immunization Programmes (NIP) in countries in Asia. Two rotavirus vaccine candidates are currently licensed and have been demonstrated to be safe, well tolerated and highly efficacious. Several additional vaccines are in the late stages of development. The conference participants agreed that decisions on the introduction of rotavirus vaccines may require additional disease burden data in some countries and that economic evaluations will help policymakers reach decisions on nationwide rotavirus vaccine implementation. Other potential issues that arise with vaccine implementation, for example, the concomitant use of rotavirus vaccines with other vaccines, were also discussed. Rotavirus vaccines have the potential to substantially reduce morbidity and mortality from rotavirus disease and impact children's health in Asia.

Diarrhoeagenic Escherichia coli and other causes of childhood diarrhoea: a case-control study in children living in a wastewater-use area in Hanoi, Vietnam

A case-control study was conducted to identify the aetiology of diarrhoeal diseases in pre-school children in a suburban area of Hanoi where the use of untreated wastewater in agriculture and aquaculture is a common practice. Stool specimens and clinical information were collected from 111 pairs of children with diarrhoea and healthy controls. A total of 73 cases (66 %) and 41 controls (36 %) had an enteric pathogen. The pathogens most often associated with diarrhoea were rotavirus (17 % of cases) and Entamoeba histolytica (15 %), followed by Shigella (5 %). Diarrhoeagenic Escherichia coli (DEC) was found in 23 % of both patients and controls. Characterization of DEC by serotyping, antimicrobial susceptibility test and PFGE showed that DEC represented by different pathotypes belonged to various serotypes. Except for three enterotoxigenic E. coli strains, typing by PFGE revealed no correlation between pathotype and serotype of DEC strains. This suggests a high prevalence of a variety of DEC subtypes in this area. For this particular region, vaccine development strategies targeting rotavirus and Shigella are likely to be of public health benefit, whereas the role of DEC and preventive measures need to be further elaborated.

Sequence analysis of the VP7 gene of human rotavirus G1 isolated in Japan, China, Thailand, and Vietnam in the context of changing distribution of rotavirus G-types

Over the last decade, rotavirus G1 has represented the most common genotype worldwide. Since 2000, the prevalence of rotavirus G1 has decreased in some countries such as Japan and China. To monitor the trend of the VP7 encoding gene of rotavirus G1, we performed a sequence analysis of 74 G1 rotavirus strains isolated in Japan, China, Thailand, and Vietnam during the period from 2002 to 2005. The phylogenetic tree showed that all of the studied G1 strains from the four countries clustered into lineage III, the same as the majority of the G1 strains isolated in China and Japan in 1990 and 1991. Examination of the deduced amino acid sequences of the G1 strains from China and Japan revealed an amino acid substitution at position 91 (Asn instead of Thr) in antigenic region A when compared to the G1 strains isolated in China and Japan in 1990, 1991, and global reference strains. For the G1 strains from Thailand and Vietnam, there were three amino acid substitutions, not belonging to any antigenic regions. The study showed that there have been no considerable changes of human rotavirus G1 isolated in Japan, China, Thailand, and Vietnam. Further studies need to be carried out for a better understanding of why such changes in the prevalence of rotavirus G1 occur in these countries.

Diversity of viruses associated with acute gastroenteritis in children hospitalized with diarrhea in Ho Chi Minh City, Vietnam

A molecular epidemiological study on common diarrheal viruses was conducted in Ho Chi Minh City, Vietnam between October 2002 and September 2003. Fecal samples were collected from 1,010 hospitalized children with acute gastroenteritis. Those samples were screened for groups A, B, and C rotavirus, adenovirus, genogroups I and II norovirus (NoV), sapovirus (SaV), and human astrovirus (HAstV) by RT-multiplex PCR, and the positive specimens were characterized further by ELISA, nested PCR, or sequencing. Among the diarrheal viruses detected, group A rotavirus was the most common, with a proportion of 67.4%, whereas NoV GII, adenovirus, SaV, and HAstV were also found in 5.5, 3.2, 0.8, and 0.6%, respectively. It is noteworthy that the group C rotavirus was first reported in Vietnam, with a proportion of 0.5% in this study. Fifty-six of 1,010 (5.5%) samples were found positive with more than one viral agent, in which 25 samples contained both group A rotavirus and NoV GII. Group A rotavirus could be identified throughout year with the peaks in both the dry and rainy season, whereas other viruses prevailed mainly in the rainy season. G-typing for the group A rotavirus showed that genotype 1 was still the most prevailing (33.0%), but interestingly, serotype 9 was emergent and became the third most common rotavirus G-type in these samples (13.7%). The four most common G-P combinations globally, G1P[8], G2P[4], G3P[8], and G4P[8] were found in 46.8% of rotavirus-positive samples, and it is of interest that one unusual rotavirus G9P[19] strain was first detected in Vietnam. The majority of NoV strains belonged to GII/4, and SaV strains mainly clustered with the Manchester strain (GI/1). Twenty-seven out of 32 adenovirus strains were identified as serotype 41. All HAstVs belonged to genotype 1. The results indicated clearly the impact of viral agents causing gastroenteritis and the importance of vaccination against diarrhea in Vietnam.

Prevalence of G2P[4] and G12P[6] rotavirus, Bangladesh

Rotavirus strains not covered by licensed vaccines are increasing.

Approximately 20,000 stool specimens from patients with diarrhea visiting an urban and a rural hospital in Bangladesh during January 2001–May 2006 were tested for group A rotavirus antigen, and 4,712 (24.0%) were positive. G and P genotyping was performed on a subset of 10% of the positive samples (n = 471). During the 2001–2005 rotavirus seasons, G1P[8] (36.4%) and G9P[8] (27.7%) were the dominant strains, but G2[4] and G12P[6] were present in 15.4% and 3.1% of the rotavirus-positive patients, respectively. During the 2005–06 rotavirus season, G2P[4] (43.2%) appeared as the most prevalent strain, and G12P[6] became a more prevalent strain (11.1%) during this season. Because recently licensed rotavirus vaccines are specific for only P[8], these vaccines may not perform well in settings where non-P[8] types are prevalent.

Risk factors for intussusception in infants in Vietnam and Australia: adenovirus implicated, but not rotavirus

OBJECTIVE

This study aimed to investigate risk factors for the development of intussusception in infants in a developing country with a suspected high incidence and in a developed country with a low incidence.

STUDY DESIGN

A prospective case-control study of infants <2 years of age with idiopathic intussusception confirmed by air enema or surgery was conducted at the National Hospital of Paediatrics (NHP), Vietnam (n = 533) and the Royal Children's Hospital (RCH), Australia (n = 51). Diagnosis was validated in a subset (84% NHP; 67% RCH) by an independent blinded radiologist. Risk factor assessment was performed using a standardized questionnaire. Stool specimens were assayed for bacterial, viral, and parasitic agents.

RESULTS

The incidence of intussusception in Vietnam was 302/100,000 in infants <1 year of age (95% CI: 258-352), substantially higher than in Australia (71/100,000). A strong association with adenovirus infection was observed at both sites (cases positive at NHP: 34%, OR 8.2; cases positive at RCH: 40%, OR 44). No association was identified between intussusception and rotavirus, other enteric pathogens, oral polio vaccine, feeding practices, or living conditions.

CONCLUSIONS

The incidence of intussusception in infants was markedly higher in Vietnam than in Australia. A strong association between adenovirus infection and intussusception was identified at both sites suggesting that adenovirus may play a role in the etiology of intussusception.

The burden of rotavirus diarrhea in Khanh Hoa Province, Vietnam: baseline assessment for a rotavirus vaccine trial

BACKGROUND

In Vietnam, rotavirus is seen as a priority disease because studies have demonstrated that >50% of children hospitalized for treatment of diarrhea have rotavirus as the pathogen. To anticipate the availability of new vaccines, we have examined our field area in Nha Trang, Khanh Hoa Province, Vietnam, as a potential site to conduct a field trial of a future rotavirus vaccine.

METHODS

Data from a population census, incidence rates of diarrhea from a previous cholera vaccine trial and hospitalization rates from computerized records collected from the 2 main hospitals in the province were reviewed to estimate the burden of rotavirus-related diarrhea that might be expected during a field trial of a rotavirus vaccine.

RESULTS

For a birth cohort of approximately 5000 children, we would expect approximately 2500 clinic visits and 650-850 hospitalizations for treatment of diarrhea, of which approximately 375-425 would be attributable to rotavirus. For the Vietnamese birth cohort of 1,639,000 children, these numbers translate into approximately 820,000 clinic visits, 122,000-140,000 hospitalizations and 2900-5400 deaths annually attributable to rotavirus-related diarrhea.

CONCLUSIONS

Vietnam is an early adaptor of new vaccines, has high national coverage rates (>85%) for childhood immunization and receives international donor support for the introduction of new vaccines. We found the epidemiologic features of rotavirus in rural Vietnam to be more similar to those of rotavirus in a developed country than to those of rotavirus in India or Bangladesh.