Biomedical subjects

Zhi-Yi Xu

Publications and source records attributed to Zhi-Yi Xu.

9 recordsLinked to original sources

PubMed2006

Implementation of good clinical practice guidelines in vaccine trials in developing countries.

The practicalities when applying the ICH GCPs (International Conference on Harmonization 1996 Good Clinical Practices [EU, MHLW, FDA. International Conference on Harmonization Guideline for Good Clinical Practice; 1997] in less developed countries (ldcs) are seldom discussed and we found no guidelines as how to "adapt" them. Below we illustrate how ICH GCP principles can be implemented in different settings. We have recently conducted in Asia (Hechi, China; Karachi, Pakistan; Hue, Vietnam; North Jakarta, Indonesia and Kolkata, India) large-scale cluster-randomized effectiveness evaluations of the Vi polysaccharide typhoid fever vaccine (Vi PS project) among approximately 200,000 individuals(1)[Acosta CJ, Galindo CM, Ali M, Abu-Elyazeed R, Ochiai RL Danovaro-Holliday MC et al. 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. TMIH 2005;10(12):1219-1228]. There is no doubt on the importance of ICH GCP in its contribution to ethical and scientifically sound clinical research. However, when the ICH GCP is implemented in ldcs some considerations must be made in order to adequately tailor them. Vaccine trials in ldcs are a frequent setting for such challenges because of the increased global interest conducting health research in such countries. The ICH GCP principles are discussed below within the framework of this recent typhoid fever vaccine study experience.

Developing Countries↗

PubMed2006

Long-term immunogenicity after single and booster dose of a live attenuated hepatitis A vaccine: results from 8-year follow-up.

Live, attenuated hepatitis A vaccines are used widely in China but there is uncertainty regarding the persistence of vaccine-induced anti-HAV antibodies after single dose and booster dose administrated at month 12. A large scale clinical trial to evaluate the live, attenuated hepatitis A vaccine was conducted in Hebei province between 1996 and 1999. Five years after the trials, children in single dose and booster dose groups were bled and followed. Seventy two percent (61/85) of children who received a single trial dose had detectable anti-HAV antibodies for 96 months (GMC at 96 months: 89.0 mIU/mL). In the booster group 98% (48/49) children remained anti-HAV positive with GMC of 262.8 mIU/mL at month 96. The reinjection with live attenuated HAV vaccine can elicit a booster effect. Results from single dose group seems not to support the need for booster doses of live attenuated hepatitis A vaccine in immunocompetent individuals regarding the persisting anti-HAV and anamnestic response of a single dose vaccine. Continued monitoring of anti-HAV antibodies is needed for a rational hepatitis A immunization strategy in China.

Alanine Transaminase↗

PubMed2006

A hospital-based surveillance for Japanese encephalitis in Bali, Indonesia.

BACKGROUND: Japanese encephalitis (JE) is presumed to be endemic throughout Asia, yet only a few cases have been reported in tropical Asian countries such as Indonesia, Malaysia and the Philippines. To estimate the true disease burden due to JE in this region, we conducted a prospective, hospital-based surveillance with a catchment population of 599,120 children less than 12 years of age in Bali, Indonesia, from July 2001 through December 2003. METHODS: Balinese children presenting to any health care facility with acute viral encephalitis or aseptic meningitis were enrolled. A "confirmed" diagnosis of JE required the detection of JE virus (JEV)-specific IgM in cerebrospinal fluid, whereas a diagnosis of "probable JE" was assigned to those cases in which JEV-specific IgM was detected only in serum. RESULTS: In all, 86 confirmed and 4 probable JE cases were identified. The annualized JE incidence rate was 7.1 and adjusted to 8.2 per 100,000 for children less than 10 years of age over the 2.5 consecutive years of study. Only one JE case was found among 96,920 children 10-11 years old (0.4 per 100,000). Nine children (10%) died and 33 (37%) of the survivors had neurological sequelae at discharge. JEV was transmitted in Bali year-round with 70% of cases in the rainy season. CONCLUSION: JE incidence and case-fatality rates in Bali were comparable to those of other JE-endemic countries of Asia. Our findings contradict the common wisdom that JE is rare in tropical Asia. Hence, the geographical range of endemic JE is broader than previously described. The results of the study support the need to introduce JE vaccination into Bali.

Child↗

PubMed2005

Incidence of diarrhea caused by rotavirus infections in rural Zhengding, China: prospective, population-based surveillance.

Rotavirus is the pathogen most commonly associated with severe gastroenteritis in young children in the People's Republic of China, yet there are few population-based data on the incidence of rotavirus infection. The present study investigated the burden of rotavirus diarrhea and rotavirus infections in rural China, according to age. Population-based surveillance was used to study the incidence of rotavirus infection among children <5 years of age in 4 townships of Zhengding County, Hebei Province, China. The total population in the catchment area in 2002 was 75,630 individuals, including 2997 children aged <5 years. Stool samples were obtained and were tested for rotavirus antigen by use of an enzyme-linked immunosorbent assay. During 2002, a total of 2010 cases of diarrhea were detected among children <5 years of age. The incidence of treated cases of diarrhea was 671 cases/1000 children/year for children <5 years of age, and it was highest for children <12 months of age (1467 cases/1000 children/year). The estimated incidence of rotavirus infection was 151 cases/1000 children/year for children <5 years of age. The highest incidence of rotavirus infection was among children aged 1-2 years (340 cases/1000 children/year). Widespread immunization of children against rotavirus before 6 months of age should be considered for the control of rotavirus diarrhea.

Child, Preschool↗

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↗

PubMed2005

Occurrence of shigellosis in the young and elderly in rural China: results of a 12-month population-based surveillance study.

In 2002, population- and treatment center-based surveillance was used to study the disease burden of shigellosis in rural Hebei Province in the People's Republic of China. A total of 10,105 children with diarrhea or dysentery were enrolled. Infants were treated most frequently for diarrhea (1,388/1,000/year) followed by children < or = 5 years old (618/1,000/year). Shigellosis was treated most often in children 3-4 years old (32/1,000/year) and people > 60 years of age (7/1,000/year). Fifty-six percent (184 of 331) Shigella isolates were detected in patients who had non-bloody diarrhea. Shigella flexneri was identified in 93% of 306 isolates. The most common S. flexneri serotypes were 1a (34%), X (33%), and 2a (28%). More than 90% of the Shigella isolates were resistant to cotrimoxazole and nalidixic acid, but remained susceptible to ciprofloxacin, norfloxacin, and gentamicin. Widespread resistance to antibiotics adds urgency to the development and use of vaccines to control shigellosis.

Adolescent↗

PubMed2004

A community-based cluster survey on preferences for treatment of diarrhoea and dysentery in Zhengding county, Hebei province, China.

Passive surveillance on the burden of disease due to diarrhoea will underestimate the burden if families use healthcare providers outside the surveillance system. To study this issue, a community-based cluster survey was conducted during October 2001 in the catchment area for a passive surveillance study in Zhengding county, a rural area of northern China. Interviews were conducted at 7 randomly-selected households in each of 39 study villages. The respondents indicated where they sought initial care for cases of diarrhoea or dysentery among children or adults. In the absence of diarrhoea and dysentery cases in the household in the preceding four weeks, the respondents were asked about healthcare use for a hypothetical case. Overall, 80% (95% confidence interval [CI] 67-93%) would chose the village clinic, 11% village pharmacy (95% CI 1-22%), 4% township hospital (95% CI -1-10%), 4% self-treatment (95% CI 1-8%), and 1% county hospital (95% CI 0-2%). Approximately, 84% of patients would seek treatment for diarrhoea and dysentery at centres participating in passive surveillance, suggesting that passive surveillance will provide a relatively accurate assessment of burden of diarrhoea in Zhengding county.

Adult↗

PubMed2004

The role of epidemiology in the introduction of vi polysaccharide typhoid fever vaccines in Asia.

Despite the availability of at least two licensed typhoid fever vaccines--injectable sub-unit Vi polysaccharide vaccine and live, oral Ty21a vaccine--for the last decade, these vaccines have not been widely introduced in public-health programmes in countries endemic for typhoid fever. The goal of the multidisciplinary DOMI (Diseases of the Most Impoverished) typhoid fever programme is to generate policy-relevant data to support public decision-making regarding the introduction of Vi polysaccharide typhoid fever immunization programmes in China, Viet Nam, Pakistan, India, Bangladesh, and Indonesia. Through epidemiological studies, the DOMI Programme is generating these data and is offering a model for the accelerated, rational introduction of new vaccines into health programmes in low-income countries. Practical and specific examples of the role of epidemiology are described in this paper. These examples cover: (a) selection of available typhoid fever vaccines to be introduced in the programme, (b) generation of policy-relevant data, (c) providing the 'backbone' for the implementation of other multidisciplinary projects, and (d) generation of unexpected but useful information relevant for the introduction of vaccines. Epidemiological studies contribute to all stages of development of vaccine evaluation and introduction.

Asia↗

PubMed2000

H2 strain attenuated live hepatitis A vaccines:protective efficacy in a hepatitis A outbreak.

AIM:To investigate the protective efficacy of H2 strain attenuated live hepatitis A vaccines (H2-strain vaccines) in hepatitis A (HA) outbreaks.METHODS:With the permission of their parents, 5551 pre-school and grade 1-3 primary school children were inoculated with 1 dose (10(6.5) TCID(50)) of H2 strain vaccines in a nonrandomized, controlled trial conducted in Fucheng County, Hebei Province in May 1997.Another 6485 children in the same grades and compatible in gender and age were enrolled as controls. Epidemiological and serological survey was conducted to evaluate the protective efficacy of the vaccines. ELISA was used to detect serum IgM anti-HAV.RESULTS:HA outbreak started in early May 1998, peaked in the middle of the same month, and lasted about 80 days. Overall 302 HA cases were found, 192(63.58%) were 5-9 years old. One vaccinee and 25 control cases were found to have hepatitis A, which account for 0.28% (1/356) and 5.92% (25/422) of all vaccinees and controls in the 14 villages, respectively. The protective efficacy of vaccines was 95.27% (95% CI: 85.83%-104.72%). In subjects tested for anti-HAV IgM from 13 villages, 1(0.40%) overt and 11(4.06%) asymptomatic HAV cases were found in 271 vaccinees but 21(6.69%) of overt and asymptomatic ones were found in 314 controls.CONCLUSION:H2 strain vaccines were excellent in preventing overt hepatitis A,but not so effective in preventing asymptomatic hepatitis A virus infection.A booster dose might be needed to get permanent reliable immunity.

Journal Article↗