Tolerance to vancomycin exists in the population of pneumococci. Tolerant isolates are associated with meningitis of increased mortality, and these isolates can be tracked by specific marker sequences in 2 genes.
Background
Varicella vaccine is now frequently administered to HIV-infected children who remain relatively healthy because it has been shown to be safe and immunogenic, but its effectiveness for this population remains unknown.
Methods
The effectiveness of varicella vaccine in preventing varicella and/or herpes zoster in HIVinfected children was assessed by chart review at two pediatric academic medical centers. These children had proven HIV infection, were receiving antiretroviral therapy, and were closely monitored between 1989 and 2007. Records were examined for immunologic data, antiretroviral therapy, varicella immunization, and the development of varicella or zoster. The vaccine's effectiveness for varicella and for zoster was calculated by subtracting from one, rate-ratios for the incidence rates of varicella or zoster in vaccinated vs. unvaccinated children.
Results
The effectiveness of varicella vaccine for preventing varicella was 82% (95% CI: 24%–99%; p = 0.01) and for preventing zoster was 100% (95% CI 67%–100%; p<0.001). When only those receiving highly active antiretroviral therapy (HAART) were included in this analysis (to assess effectiveness of vaccine independent of the effect of HAART), the vaccine's effectiveness against zoster was 100% (95% CI: 63%–100%; p=0.001).
Conclusion
Varicella vaccine is highly effective in preventing both varicella and zoster in HIV-infected children.
Current HIV guidelines recommend monitoring CD4 counts every 3-4 months. In the era of highly active antiretroviral therapy (HAART) and HIV PCR, this retrospective study reexamines the required frequency of the CD4 assay. Predictor variables, including age, previous CD4 count, HIV viral load (VL), time interval since last VL and CD4 count (TINT), and antiretroviral history, were abstracted. A recursive partitioning-based regression tree analysis was used to determine if the absolute current CD4 count was above or below the age appropriate Pneumocystis jiroveci pneumonia (PCP) prophylaxis cutoff. We analyzed concurrently obtained VLs and CD4 count including 601 results from 43 HIV-infected children aged 1-<6 years (Group I) and 1,364 results from 93 children/adolescents 6-<23 years (Group II). Using 75% of observations to build a predictive model (learning dataset), the ability to correctly predict the range of the outcome variable in the remaining 25% of observations (training dataset) was 93% in Group I and 97% in Group II. Predictor variables included age, recent VL and CD4 count, and TINT. A total of 1,000 repeats of this model building using randomly selected observations showed a correct predictive ability of 89.6% [standard error (SE) 2.3%] in Group I and 95.6% (SE 1%) in Group II. The ability of a classification tree to determine if the current CD4 count is above or below the age-specific cutoff for PCP prophylaxis is very good and allows less frequent CD4 assays. The principles underlying this modeling-based approach have broad applicability and cost saving implications.
A nucleic acid sequence-based amplification (NASBA) assay that detects HIV RNA may be helpful in excluding perinatal HIV infection. We reviewed the records of 190 infants born to HIV-infected mothers. The sensitivity and specificity of the NASBA assay were 100% when measured at two time periods in the first 9 months of life. The HIV RNA NASBA assay should be considered a valid diagnostic test in this population.
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