Further observations on the immune response to recombinant hepatitis B vaccine after administration to aboriginal and Torres Strait Island children.

OBJECTIVE: To determine the prevalence of markers of hepatitis B virus (HBV) immunity and infection at 5 years of age in Aboriginal and Torres Strait Island children who were fully vaccinated in infancy, and to examine the response to a booster dose of hepatitis B vaccine in those children who had no detectable immunity despite vaccination. METHODOLOGY: A cross-sectional study of serological markers to HBV in a sample of 239 Aboriginal and Torres Strait Island children, with a mean age of 5.7 years, who were fully vaccinated in infancy. The antibody response to a booster dose of hepatitis B vaccine was determined in those children in the sample who had no markers of either immunity to HBV or infection with HBV. RESULTS: Of the 239 children, 6% (95% CI 4-10%) had been infected and, of these, four were HBV surface antigen (HBsAg) positive. Of the remaining 224 children, only 41% (95% CI 35-48%) had evidence of immunity (i.e. an antibody to HBV surface antigen (anti-HBs) level of > or = 10 miu/mL) to HBV. Of the children with no detectable immunity (i.e. anti-HBs < 10 miu/mL), 113 were followed up after receiving a booster dose of hepatitis B vaccine. Of these, 84% (95% CI 76-90%) had an anamnestic response (i.e. anti-HBs < 10 miu/mL following the booster dose). Therefore 16% (95% CI 10-24%) still had no detectable immunity following the booster dose. CONCLUSIONS: This study provides further evidence that Aboriginal and Torres Strait Island children have a suboptimal response to recombinant hepatitis B vaccine. It also indicates that a considerable number of Aboriginal and Torres Strait Island children in the study age cohort have been exposed to HBV. However, despite these concerns, this study and historical data provide strong evidence that there has been a marked reduction in the prevalence of HBV infection and carriage in previously 'high risk' Aboriginal and Torres Strait Island children since the introduction of hepatitis B vaccines. Aboriginal and Torres Strait Island children who have been fully vaccinated in infancy do not require a booster dose of hepatitis B vaccine at school entry.

Immunity to hepatitis B, poliomyelitis and measles in fully vaccinated aboriginal and Torres Strait Island children.

OBJECTIVE: To determine the immunity to hepatitis B, poliomyelitis and measles in fully vaccinated Aboriginal and Torres Strait Island children in north Queensland. METHODOLOGY: A cross-sectional survey of immunity in a sample of children; 101 fully vaccinated Aboriginal and Torres Strait Island children, with a median age of 24.5 months, from 10 communities in North Queensland participated in this study. The main outcome measures were the prevalence of adequate antibody levels against hepatitis B, poliomyelitis and measles. RESULTS: Only 54% (95% CI 44-63%) of the children had adequate immunity (> or = 10 m iu/mL) to hepatitis B, and one child had been infected despite vaccination. Although all the children (95% CI 96-100%) had adequate immunity (i.e. neutralizing antibodies at a dilution of > or = 1:8) to poliovirus 2, only 93% (95% CI 86-96%) and 60% (95% CI 50-69%) had adequate immunity to polioviruses 1 and 3, respectively. Nearly all (96%; 95% CI 90-98%) of the children had adequate immunity (i.e. detectable IgG antibody) to measles. CONCLUSIONS: Although a relatively low proportion of the children had adequate antibody levels against hepatitis B the clinical significance of this observation is uncertain. Further studies are needed to determine whether fully vaccinated Torres Strait Island children have been adequately protected and whether they require a booster dose of hepatitis B vaccine. A substantial proportion of fully vaccinated Aboriginal and Torres Strait Island children are inadequately protected against poliomyelitis, and therefore any such child with acute flaccid paralysis should be investigated fully for poliomyelitis. Vaccinated Aboriginal and Torres Strait Island children are well protected against measles, as are other Australian children.

A new confirmatory Neisseria gonorrhoeae real-time PCR assay targeting the porA pseudogene.

The Roche Cobas Amplicor system is widely used for the detection of Neisseria gonorrhoeae but is known to cross react with some commensal Neisseria spp. Therefore, a confirmatory test is required. The most common target for confirmatory tests is the cppB gene of N. gonorrhoeae. However, the cppB gene is also present in other Neisseria spp. and is absent in some N. gonorrhoeae isolates. As a result, laboratories targeting this gene run the risk of obtaining both false-positive and false-negative results. In the study presented here, a newly developed N. gonorrhoeae LightCycler assay (NGpapLC) targeting the N. gonorrhoeae porA pseudogene was tested. The NGpapLC assay was used to test 282 clinical samples, and the results were compared to those obtained using a testing algorithm combining the Cobas Amplicor System (Roche Diagnostics, Sydney, Australia) and an in-house LightCycler assay targeting the cppB gene (cppB-LC). In addition, the specificity of the NGpapLC assay was investigated by testing a broad panel of bacteria including isolates of several Neisseria spp. The NGpapLC assay proved to have comparable clinical sensitivity to the cppB-LC assay. In addition, testing of the bacterial panel showed the NGpapLC assay to be highly specific for N. gonorrhoeae DNA. The results of this study show the NGpapLC assay is a suitable alternative to the cppB-LC assay for confirmation of N. gonorrhoeae-positive results obtained with Cobas Amplicor.

Comparison of four methods for quantitative measurement of hepatitis B viral DNA.

AIMS/METHODS: Four assays for measuring HBV-DNA quantitatively have been compared with regard to sensitivity, precision and linearity. The methods were 125I-labelled solution hybridisation assay (liquid hybridisation, Abbott), an ELISA-based chemiluminescent RNA-DNA hybrid assay (RNA-DNA, Digene), a chemiluminescent branching oligonucleotide assay (bDNA, Chiron) and a membrane hybridisation assay using slot-blot equipment (slot blot). RESULTS: The bDNA assay was linear over three orders of magnitude and was the most sensitive assay, being approximately ten times more sensitive than the other assays, so that samples negative on RNA-DNA, liquid hybridisation and slot blot gave quantifiable results on bDNA. Furthermore, intra- and inter-assay variability showed that the bDNA and liquid hybridisation assays had the greatest precision, with coefficients of variation of 6.6% to 11.5% and 2.3% to 10.5%, respectively. However, the nominated amounts of HBV DNA in the standards (from all assays) were not reproducible in the other assays, such that amounts measured with bDNA would give values approximately twice that of RNA-DNA and 60 times that of liquid hybridisation. CONCLUSIONS: The recently developed bDNA assay has advantages compared with the other assays in quantitating samples with low levels of virus present. In addition, since the assays vary considerably by a number of criteria, the method of measurement should always be reported.