A field study of the safety and efficacy of two candidate rotavirus vaccines in a Native American population

Article Abstract:

In developing countries, diarrhea is a serious, and often fatal, illness. Of the various organisms that cause diarrhea, those caused by the rotavirus are the most serious, and the development of a vaccine against the rotavirus strain is a top priority. Two vaccines have been developed - a bovine strain known as RIT 4237 and a rhesus monkey rotavirus (RRV) - but each has been shown to have different levels of effectiveness, depending upon the population it is tested on. The effectiveness of the two vaccines has never been directly compared in one population. To address this last issue, a study was conducted using a sample of the Navaho population in Arizona. A total of 321 infants and their parents participated in this study and the infants were randomly divided into one of three groups - 108 were in the RRV group, 106 were in the RIT 4237 group, and 107 were in a group that received only a placebo. Participants were followed for a total of 17 months, during which time parents recorded incidence of diarrhea and provided stool samples to researchers. It was found that in this population neither vaccine was more effective than the inert placebo alone in preventing diarrhea. In the RRV group, 10.2 percent of the infants developed diarrhea during the study period, while 10.4 percent developed diarrhea in the RIT 4237 group, and 8.4 percent developed diarrhea in the placebo group. In light of the fact that each vaccine has been shown effective in some other populations, this provides further evidence that the vaccines seem to be selectively effective, but the results shed little light on the comparative effectiveness of the vaccines. (Consumer Summary produced by Reliance Medical Information, Inc.)

Complications and side effects, Diseases, Developing countries, Diarrhea, Navajos

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Effect of breast-feeding on oral rhesus rotavirus vaccine seroconversion: a metaanalysis

Article Abstract:

Rotavirus is responsible for numerous cases of diarrhea and intestinal inflammation in infants and small children. To insure protection against rotavirus infection, rotavirus vaccine should be administered to infants during the first four months of life. Breast-feeding is common during early infancy, and it may provide some protection against rotavirus-induced diarrhea during the first six months of life. The exact mechanism by which this protection is conferred is not know. Breast milk may contain rotavirus antibodies or other nonspecific inhibitors that may be responsible for the protective effect. The effect of breast-feeding on the effectiveness of rhesus (monkey) rotavirus vaccine (RRV) in infants two to four months of age was determined. Three separate study trials were conducted. Each study trial included breast-fed and bottle-fed infants. Serum samples were collected from the infants four weeks before and four weeks after vaccination, and analyzed for the presence of rotavirus. If rotavirus was detected in serum following vaccination, then the serum was said to be seroconverted, meaning that the vaccination was effective. The results from three different studies were combined. Seroconversion occurred in 42 of 88 breast-fed infants (48 percent), and in 62 of 88 bottle-fed infants (70 percent). These results suggest that breast feeding confers an an adverse effect on RRV. It is possible that breast milk may contain antibodies to rotavirus that reduce the effectiveness of the vaccine. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Breast feeding, Rotaviruses

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Development of dengue and Japanese encephalitis vaccines

Article Abstract:

The World Health Organization sponsored a meeting to discuss the development of vaccines for dengue and Japanese encephalitis (JE, inflammation of the brain). Dengue disease is most prevalent in tropical and subtropical regions. It is caused by the dengue virus, and is transmitted by mosquitos. Infection results in hemorrhagic fever, and symptoms include fever, gastrointestinal bleeding, circulatory failure and shock. Roughly 40 million cases of dengue and 30,000 cases of JE are reported annually. JE is caused by an agent know as flavivirus, which is an RNA virus (it uses RNA instead of DNA as its genetic material). Infection with flavivirus may cause encephalitis or hemorrhagic fever. Current research is focusing on the development of vaccines for dengue and JE. Vaccine development has been hampered by the lack of specific animal models of dengue disease and JE. Human studies are the only certain method for determining the effectiveness of a vaccine. Recent human trials of dengue vaccines in Thailand have been successful. The development of a live attenuated dengue vaccine may soon be realized. In addition, studies using genetic engineering methods have yielded a recombinant (recombination of genes from flavivirus) vaccine. Human trials using recombinant vaccines are scheduled to begin shortly. The vaccine will be tested on patients with type 4 dengue disease, the final and most severe stage of infection. (Consumer Summary produced by Reliance Medical Information, Inc.)

Disease transmission, Dengue, Dengue fever, Dengue viruses, Dengue virus, Flaviviruses

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