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S Carter-Campbell

Publications and source records attributed to S Carter-Campbell.

4 recordsLinked to original sources
PubMed1997

A partially grouped logrank test.

We propose a modified version of the standard logrank test for survival data in which the first contribution to the statistic is based on grouping of data before a pre-selected grouping time. The grouping is accomplished by artificially constructing the first table based on the product limit estimates of the proportions surviving at the grouping time. Remaining contributions to the statistic are identical to that of the standard logrank statistic. The approach has the advantage of being uninfluenced by non-proportional hazards differences prior to the grouping time while being almost as efficient as the usual logrank test for proportional-hazards alternatives. The statistic is particularly useful for interim monitoring in situations where early difference between treatments are unimportant and/or lagged treatment effects are anticipated. We report simulation studies to verify and investigate the test's properties.

Bone Marrow Transplantation↗
PubMed1996

Rotavirus infection in infants as protection against subsequent infections.

BACKGROUND: Rotavirus is the leading cause of severe diarrhea in infants. To provide a base line for assessing the efficacy of rotavirus vaccines, we evaluated the protection that is conferred by natural rotavirus infection. METHODS: We monitored 200 Mexican infants from birth to two years of age by weekly home visits and stool collections. A physician assessed the severity of any episodes of diarrhea and collected additional stool specimens for testing by enzyme immunoassay and typing of strains. Serum collected during the first week of life and every four months thereafter was tested for antirotavirus IgA and IgG. RESULTS: A total of 316 rotavirus infections were detected on the basis of the fecal excretion of virus (56 percent) or a serologic response (77 percent), of which 52 percent were first and 48 percent repeated infections. Children with one, two, or three previous infections had progressively lower risks of both subsequent rotavirus infection (adjusted relative risk, 0.62, 0.40, and 0.34, respectively) and diarrhea (adjusted relative risk, 0.23, 0.17, and 0.08) than children who had no previous infections. No child had moderate-to-severe diarrhea after two infections, whether symptomatic or asymptomatic. Subsequent infections were significantly less severe than first infections (P=0.024), and second infections were more likely to be caused by another G type (P=0.054). CONCLUSION: In infants, natural rotavirus infection confers protection against subsequent infection. This protection increases with each new infection and reduces the severity of the diarrhea.

Antibodies, Bacterial↗
PubMed1995

Effect of maternal rotavirus immunization on milk and serum antibody titers.

This prospective study evaluated human milk and serum antirotavirus antibody concentrations following maternal rotavirus immunization. Postpartum women (33) were randomized into 3 groups and received a single oral dose of rhesus rotavirus monovalent reassortant vaccine (10(4) pfu), tetravalent vaccine (10(4) pfu), or placebo. Milk (secretory [s] IgA) and serum (IgA and IgG) specimens were tested for antirotavirus isotype-specific antibody. Sera also were tested for G1- to G4-specific antibody. Prevaccine milk and serum isotype-specific antibody concentrations were not significantly different in the 3 groups. Postvaccine sIgA log titers were significantly greater in the 2 vaccine groups than the placebo group (P = .002). Mean log10 titers at 1 week were 2.1 (95% confidence interval [CI], 2.0-2.3) in the 2 vaccine groups and 1.7 (95% CI, 1.5-1.9) in the placebo group. Milk titers did not differ between vaccine groups. There was no difference in reactogenicity between groups. The significantly higher milk concentrations of antibody to rotavirus in postpartum women who received rotavirus immunization persisted for 4 months.

Adolescent↗