Biomedical subjects

Do Gia Canh

Publications and source records attributed to Do Gia Canh.

14 recordsLinked to original sources

PubMed2007

Trial participation and vaccine desirability for Vi polysaccharide typhoid fever vaccine in Hue City, Viet Nam.

OBJECTIVES: To identify demand for Vi typhoid fever vaccine for school-age children; obstacles and enabling factors for vaccine delivery; and socio-behavioural factors associated with trial participation and possible predictors of future vaccine acceptance, in Hue City, Viet Nam. METHODS: Pre- and post-trial surveys of randomly selected households with children aged 6-17 years. Simple multinomial logistic analyses for ratios of relative risks (RRR) and significance on trial participation by demographics and variables related to typhoid fever, vaccination, and pre-trial experiences with information and consents. Multiple logistic regressions to assess differences in participation based on child's characteristics. RESULTS: As many as 62.6% of households let all school age children participate, 10.2% let some participate, and 26.8% let none of their children participate in the trial. Factors associated with all children participating included past use of healthcare facilities (RRR, 0.45; 95% CI, 0.24-0.83), knowledge of vaccines (RRR, 0.17; 95% CI, 0.03-0.86), and perceived causes of typhoid fever (RRR, 0.90; 95% CI, 0.81-0.99). Factors associated with some children participating included utilization of healthcare facilities (RRR, 0.08; 95% CI, 0.01-0.66) and perceived severity of typhoid fever (RRR, 0.64; 95% CI 0.46-0.88). Participation was associated with satisfaction regarding pre-vaccination information and consent procedures. Children and adolescents were active decision-makers. Only 14 of 461 (2.2%) respondents would not use the Vi vaccine in the future for their child(ren). CONCLUSIONS: Inter-related factors contribute to participation in a clinical vaccine trial, which may differ from desire to participate in a public health campaign. Educational campaigns need to be targeted to children and adolescents, and consideration for assent procedures for minors. Obtaining informed consent may affect trial participation within a social and political system unaccustomed to these procedures.

Adolescent↗

PubMed2006

Safety and immunogenicity of a reformulated Vietnamese bivalent killed, whole-cell, oral cholera vaccine in adults.

Vietnam currently produces an orally administered, bivalent (O1 and O139) killed whole-cell vaccine and is the only country in the world with endemic cholera to use an oral cholera vaccine in public health practice. In order to allow international use, the vaccine had to be reformulated to meet World Health Organization (WHO) requirements. We performed a randomized, placebo controlled, safety and immunogenicity studies of this reformulated vaccine among Vietnamese adults. One hundred and forty-four subjects received the two-dose regimen and 143 had two blood samples obtained for analysis. We found that this reformulated oral killed whole-cell cholera vaccine was safe, well tolerated and highly immunogenic.

Administration, Oral↗

PubMed2006

Long-term effectiveness against cholera of oral killed whole-cell vaccine produced in Vietnam.

We assessed the long-term protection afforded by a killed whole-cell oral cholera vaccine produced in Vietnam. A mass immunization of children and adults with the killed whole-cell oral cholera vaccine was undertaken in half of the communes of Hue, Vietnam, in 1998; the remaining communes were immunized in 2000. No cholera was observed in Hue until 2003, when an outbreak of El Tor cholera made it possible to conduct a case-control study. The overall vaccine effectiveness 3-5 years after vaccination was 50% (9-63%). This low-cost, easily administered vaccine should be considered as a tool for the control of cholera.

Administration, Oral↗

PubMed2006

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.

Child, Preschool↗

PubMed2006

A multicentre study of Shigella diarrhoea in six Asian countries: disease burden, clinical manifestations, and microbiology.

BACKGROUND: The burden of shigellosis is greatest in resource-poor countries. Although this diarrheal disease has been thought to cause considerable morbidity and mortality in excess of 1,000,000 deaths globally per year, little recent data are available to guide intervention strategies in Asia. We conducted a prospective, population-based study in six Asian countries to gain a better understanding of the current disease burden, clinical manifestations, and microbiology of shigellosis in Asia. METHODS AND FINDINGS: Over 600,000 persons of all ages residing in Bangladesh, China, Pakistan, Indonesia, Vietnam, and Thailand were included in the surveillance. Shigella was isolated from 2,927 (5%) of 56,958 diarrhoea episodes detected between 2000 and 2004. The overall incidence of treated shigellosis was 2.1 episodes per 1,000 residents per year in all ages and 13.2/1,000/y in children under 60 months old. Shigellosis incidence increased after age 40 years. S. flexneri was the most frequently isolated Shigella species (1,976/2,927 [68%]) in all sites except in Thailand, where S. sonnei was most frequently detected (124/146 [85%]). S. flexneri serotypes were highly heterogeneous in their distribution from site to site, and even from year to year. PCR detected ipaH, the gene encoding invasion plasmid antigen H in 33% of a sample of culture-negative stool specimens. The majority of S. flexneri isolates in each site were resistant to amoxicillin and cotrimoxazole. Ciprofloxacin-resistant S. flexneri isolates were identified in China (18/305 [6%]), Pakistan (8/242 [3%]), and Vietnam (5/282 [2%]). CONCLUSIONS: Shigella appears to be more ubiquitous in Asian impoverished populations than previously thought, and antibiotic-resistant strains of different species and serotypes have emerged. Focusing on prevention of shigellosis could exert an immediate benefit first by substantially reducing the overall diarrhoea burden in the region and second by preventing the spread of panresistant Shigella strains. The heterogeneous distribution of Shigella species and serotypes suggest that multivalent or cross-protective Shigella vaccines will be needed to prevent shigellosis in Asia.

Adolescent↗

PubMed2006

The feasibility of a school-based VI polysaccharide vaccine mass immunization campaign in Hue City, central Vietnam: streamlining a typhoid fever preventive strategy.

We report the coverage, safety, and logistics of a school-based typhoid fever immunization campaign that took place in Hue City, central Vietnam; a typhoid fever endemic area. A cluster-randomized evaluation-blinded controlled trial was designed where 68 schools (cluster) were randomly allocated the single dose Vi polysaccharide vaccine (Typherix) or the active control hepatitis A vaccine (Havrix). A safety surveillance system was implemented. A total of 32,267 children were immunized with a coverage of 57.5%. Strong predictors for vaccination were attending primary schools, peri-urban location of the school, and low family income. Human resources were mainly schoolteachers and the campaign was completed in about 1 month. Most adverse events reported were mild. Safe injection and safe sharp-waste disposal practices were followed. A typhoid fever school-based immunization campaign was safe and logistically possible. Coverage was moderate and can be interpreted as the minimum that could have been achievable because individual written informed consent procedures were sought for the first time in Hue City and the trial nature of the campaign. The lessons learned, together with cost-effectiveness results to be obtained by the end of follow-up period, will hopefully accelerate the introduction of Vi typhoid fever vaccine in Vietnam.

Adolescent↗

PubMed2005

Neighborhood size and local geographic variation of health and social determinants.

BACKGROUND: Spatial filtering using a geographic information system (GIS) is often used to smooth health and ecological data. Smoothing disease data can help us understand local (neighborhood) geographic variation and ecological risk of diseases. Analyses that use small neighborhood sizes yield individualistic patterns and large sizes reveal the global structure of data where local variation is obscured. Therefore, choosing an optimal neighborhood size is important for understanding ecological associations with diseases. This paper uses Hartley's test of homogeneity of variance (Fmax) as a methodological solution for selecting optimal neighborhood sizes. The data from a study area in Vietnam are used to test the suitability of this method. RESULTS: The Hartley's Fmax test was applied to spatial variables for two enteric diseases and two socioeconomic determinants. Various neighbourhood sizes were tested by using a two step process to implement the Fmaxtest. First the variance of each neighborhood was compared to the highest neighborhood variance (upper, Fmax1) and then they were compared with the lowest neighborhood variance (lower, Fmax2). A significant value of Fmax1 indicates that the neighborhood does not reveal the global structure of data, and in contrast, a significant value in Fmax2 implies that the neighborhood data are not individualistic. The neighborhoods that are between the lower and the upper limits are the optimal neighbourhood sizes. CONCLUSION: The results of tests provide different neighbourhood sizes for different variables suggesting that optimal neighbourhood size is data dependent. In ecology, it is well known that observation scales may influence ecological inference. Therefore, selecting optimal neigborhood size is essential for understanding disease ecologies. The optimal neighbourhood selection method that is tested in this paper can be useful in health and ecological studies.

Journal Article↗

PubMed2005

A multi-country cluster randomized controlled effectiveness evaluation to accelerate the introduction of Vi polysaccharide typhoid vaccine in developing countries in Asia: rationale and design.

Phase-III vaccine efficacy trials typically employ individually randomized designs intended to ensure that measurements of vaccine protective efficacy reflect only direct vaccine effects. As a result, decisions about introducing newly licensed vaccines into public health programmes often fail to consider the substantially greater protection that may occur when a vaccine is deployed in public health programmes, due to the combination of direct plus indirect vaccine protective effects. Vaccine total protection can be better evaluated with cluster randomized trials. Such a design was considered to generate policy relevant data to accelerate the rationale introduction of the licensed typhoid fever Vi polysaccharide (PS) vaccine in Asia by the Diseases of the Most Impoverished (DOMI) typhoid fever programme. The DOMI's programme multi-country study is one of the largest cluster randomized vaccine trials ever mounted in Asia, which includes approximately 200,000 individuals. Its main objective is to determine the effectiveness of a licensed Vi PS vaccine. The rationale and design of this study are discussed. Preliminary results are presented that determined the final planning of the trial before immunization. Important methodological and practical issues regarding vaccine cluster randomized designs are illustrated.

Adolescent↗

PubMed2004

Emergence and serovar transition of Vibrio parahaemolyticus pandemic strains isolated during a diarrhea outbreak in Vietnam between 1997 and 1999.

We characterized 523 Vibrio parahaemolyticus strains isolated during a survey of diarrhea patients in Khanh Hoa province, Vietnam between 1997 and 1999. Forty-nine percent of the strains were judged to belong to the pandemic strains that emerged around 1996 and spread to many countries. These strains were positive in the GS-PCR assay and carried the tdh gene. The ORF8 of the f237 phage genome, a possible marker of the pandemic clone, was absent in 10% of these strains. Eleven O: K serovars were detected among the pandemic strains and the strains representing all 11 serovars of pandemic strains were shown to be closely related regardless of the ORF8 genotype using arbitrarily primed PCR and pulsed field gel electrophoresis analyses. It was clear that a transition of major serovars occurred among the pandemic strains represented by the emergence of O3: K6 in 1997, O4: K68 in 1998, and O1: K25 in 1998 and 1999.

DNA Fingerprinting↗

PubMed2004

Effect of dosage on immunogenicity of a Vi conjugate vaccine injected twice into 2- to 5-year-old Vietnamese children.

In a double-blind, randomized, and placebo-controlled previous trial, the efficacy of Vi-rEPA for typhoid fever in 2- to 5-year-olds was 89.0% for 46 months. Vi-rEPA contained 25 microg of Vi and induced a greater-than-eightfold rise in immunoglobulin G (IgG) anti-Vi in all of the vaccinees tested. In this investigation, we conducted a dosage-immunogenicity study of 5, 12.5, and 25 microg of Vi-rEPA in this age group. Two doses of Vi-rEPA were injected 6 weeks apart. Blood samples were taken before and at 10 weeks (4 weeks after the second injection) and 1 year later. All postimmunization geometric mean (GM) levels were higher than the preimmune levels (P < 0.0001). At 10 weeks, the GM IgG anti-Vi level elicited by 25 microg (102 EU/ml) was higher than those elicited by 12.5 microg (74.7 EU/ml) and 5 microg (43 EU/ml) (P < 0.004): all of the children had > or = 3.52 EU/ml (estimated minimum protective level). One year later, the levels declined about sevenfold (13.3 and 11.3 versus 6.43 EU/ml, P < 0.0001) but remained significantly higher than the preimmune levels (P < 0.0001), and >96% of the children had a greater-than-eightfold rise. This study also confirmed the safety and consistent immunogenicity of the four lots of Vi-rEPA used in this and previous trials.

ADP Ribose Transferases↗

PubMed2004

Healthcare use for diarrhoea and dysentery in actual and hypothetical cases, Nha Trang, Viet Nam.

To better understand healthcare use for diarrhoea and dysentery in Nha Trang, Viet Nam, qualitative interviews with community residents and dysentery case studies were conducted. Findings were supplemented by a quantitative survey which asked respondents which healthcare provider their household members would use for diarrhoea or dysentery. A clear pattern of healthcare-seeking behaviours among 433 respondents emerged. More than half of the respondents self-treated initially. Medication for initial treatment was purchased from a pharmacy or with medication stored at home. Traditional home treatments were also widely used. If no improvement occurred or the symptoms were perceived to be severe, individuals would visit a healthcare facility. Private medical practitioners are playing a steadily increasing role in the Vietnamese healthcare system. Less than a quarter of diarrhoea patients initially used government healthcare providers at commune health centres, polyclinics, and hospitals, which are the only sources of data for routine public-health statistics. Given these healthcare-use patterns, reported rates could significantly underestimate the real disease burden of dysentery and diarrhoea.

Adult↗

PubMed2004

Acceptability and accessibility of a Shigellosis vaccine in Nha Trang city of Viet Nam.

The acceptability and accessibility of a hypothetical Shigella vaccination campaign was explored. A household survey was conducted with 539 randomly-selected residents of six communes in Nha Trang city of Viet Nam. Four categories of acceptability, such as refusers, low acceptors, acceptors, and high acceptors, were established, Refusers were significantly more likely to be elderly women and were less likely to know the purpose of vaccinations. Low acceptors tended to be male, elderly, and live in urban areas. Low acceptors perceived the disease as less serious and themselves as less vulnerable than acceptors and high acceptors. In terms of accessing vaccination, the commune health centre workers and commune leaders were the preferred sources of information and commune health centres the preferred location for vaccination. Direct verbal information from healthcare providers and audio-visual media were preferred to written information. The respondents expressed a desire for knowledge about the side-effects and efficacy of the vaccine. These findings are significant for targeting specific messages about shigellosis and vaccination to different populations and maximizing informed participation in public-health campaigns.

Adult↗

PubMed2003

The vaccine data link in Nha Trang, Vietnam: a progress report on the implementation of a database to detect adverse events related to vaccinations.

Real, perceived and unknown adverse events secondary to vaccinations are a source of concern for care providers of children. In the USA large linked databases have provided helpful information regarding the safety of vaccines. Very little prospectively collected data on vaccine safety is available from resource poor countries, but safety concerns may be even more relevant in such settings. Vaccine manufacturers do not have to pass the same rigorous safety standards as vaccine manufacturers in rich countries. Vaccines, which protect against cholera, Japanese encephalitis, rabies or typhoid fever are predominantly used in resource poor, tropical countries and frequently do not undergo vigorous post marketing surveillance. New vaccines specifically suited for resource poor countries are sometimes marketed without the scrutiny of vigilant, independent regulatory authorities. We describe here the design and implementation of a large linked database for a semi-rural province in central Vietnam. The design overcomes several problems inherent in data bases of medical events and vaccinations in developing countries. Assigning a permanent identification (ID) number to each resident avoids the ambiguities of ID numbers based on the address. The distribution and use of medical identification cards with a permanent ID number assists in the unambiguous identification of vaccinees and patients. Medical records of all admissions are coded according to International Classification of Diseases (ICD-10) and transcribed into a computer system. Because these processes are novel the data collected by the study will be validated. Project staff will check records on vaccinations and hospital admissions through household visits at regular intervals. Data describing vaccinations and medical events are linked to the data collected by the project staff in a computer system. Based on the validation of the data we hope to optimize this model. Once we find the model working it is planned export this vaccine data safety link to other settings of similar economic status.

Database Management Systems↗

PubMed2002

Clinical, epidemiological, and socioeconomic analysis of an outbreak of Vibrio parahaemolyticus in Khanh Hoa Province, Vietnam.

From 1996 onward, a pandemic spread of Vibrio parahaemolyticus infections due to one clone has been reported in several Asian countries. During a population-based study that relied on passive surveillance, 548 cases of V. parahaemolyticus infection were detected between 1997 and 1999 in the Khanh Hoa province of Vietnam. Detection of cases of V. parahaemolyticus infection abruptly stopped in November 1999, although Vibrio species other than V. parahaemolyticus continued to be isolated throughout 2000. Of the infections, 90% occurred in individuals >5 years old; 53% of the patients presented with watery stools, and 6% reported blood in their stools. All patients had recovered by the time of discharge. A surprising risk factor for V. parahaemolyticus infections was high socioeconomic status. Like the interruption of the transmission of V. cholerae infections that had been observed earlier, the transmission of V. parahaemolyticus came to a halt without meteorological changes or changes in water supply and sanitation.

Adolescent↗