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Context: Changes in serum vitamin D metabolites and calcium absorption with varying doses of oral vitamin D3 in healthy children are unknown. Objective: Our objective was to examine the dose-response effects of supplemental vitamin D3 on serum vitamin D metabolites and calcium absorption in children living at two U.S. latitudes. Design: Black and white children (n = 323) participated in a multisite (U.S. latitudes 34° N and 40° N), triple-masked trial. Children were randomized to receive oral vitamin D3 (0, 400, 1000, 2000, and 4000 IU/d) and were sampled over 12 weeks in winter. Serum 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)2D) were measured using RIA and intact PTH (iPTH) by immunoradiometric assay. Fractional calcium absorption was determined from an oral stable isotope 44Ca (5 mg) in a 150-mg calcium meal. Nonlinear and linear regression models were fit for vitamin D metabolites, iPTH, and calcium absorption. Results: The mean baseline 25(OH)D value for the entire sample was 70.0 nmol/L. Increases in 25(OH)D depended on dose with 12-week changes ranging from −10 nmol/L for placebo to 76 nmol/L for 4000 IU. Larger 25(OH)D gains were observed for whites vs blacks at the highest dose (P < .01). Gains for 1,25(OH)2D were not significant (P = .07), and decreases in iPTH were not dose-dependent. There was no dose effect of vitamin D on fractional calcium absorption when adjusted for pill compliance, race, sex, or baseline 25(OH)D. Conclusion: Large increases in serum 25(OH)D with vitamin D3 supplementation did not increase calcium absorption in healthy children living at 2 different latitudes. Supplementation with 400 IU/d was sufficient to maintain wintertime 25(OH)D concentrations in healthy black, but not white, children.

From 1 July 1987 to 31 December 1988, a total of 317 animals (91% of which were dogs) were confirmed to have rabies in Hermosillo, Mexico. The median age of rabid dogs was 1 year, 69% were male, and 98% were owned. The epizootic started in the southern areas of the city, rapidly involved the entire city, and persisted mainly in lower socioeconomic status areas. The area of the city and mean household size were significant predictor variables for the population density of rabid dogs around household clusters (Poisson linear regression, P0.001 and P = 0.03, resp). Approximately 2.5% of city residents were bitten by dogs in 1987, with the rate of reported dog bite injuries being positively correlated with mean household size and the proportion of households that owned dogs. Visits to the city health centre for evaluation of possible exposures to rabies increased by 135% after the start of the epizootic; approximately 273 per 100,000 city residents were administered a full or partial course of rabies post-exposure prophylaxis in 1987. Children were at greatest risk for exposures to rabies, accounting for 60% of all reported animal bite injuries evaluated at the health centre. Also they were more likely than older persons to have received bite injuries to the head, face, and neck (odds ratio = 21.6, 95% confidence interval = 5.4, 186.5).Almost all cases of human rabies result from bites by rabid dogs. Controlling dog rabies is therefore crucial for humans. 317 animals, 91% of which were dogs, were confirmed to have rabies in Hermosillo, Mexico, from July 1, 1987, to December 31, 1988. The dogs were of median age 1 year, 69% were male, and 98% were owned. The epizootic started in the southern areas of the city, spread quickly through the city, and persisted largely in lower socioeconomic status areas. Approximately 2.5% of city residents were bitten by dogs in 1987, with the rate of reported dog bite injuries positively correlated with mean household size and the proportion of households which owned dogs. Visits to the city health center for evaluation of possible exposures to rabies increased by 135% after the start of the epizootic over which approximately 273 per 100,000 city residents were administered a full or partial course of rabies post-exposure prophylaxis in 1987. Comprising 60% of all reported animal bite injuries evaluated at the center, children were at greatest risk for exposures to rabies. Children were also more likely than older people to have received bite injuries to the head, face, and neck.

Human parvovirus B19, the cause of erythema infectiosum, has recently been associated with adverse fetal outcomes. During a large outbreak of erythema infectiosum in Connecticut, a survey was conducted on 571 (90%) of 634 school and day-care personnel to determine the risk of acquiring B19 infection. Serologic evidence of B19 infection was determined by using an enzyme-linked immunosorbent assay. Of the school and day-care personnel, 58% had evidence of previous B19 infection. The minimal rate of B19 infection in susceptible personnel during the outbreak was 19%. The risk was increased for teachers and day-care providers who had contact with younger children and with greater numbers of ill children. These results suggest that B19 infection is an occupational risk for school and day-care personnel.

Myopia is common in Western populations but is considered rare in nonindustrialized population groups. However, studies in undeveloped areas of the Arctic and sub-Arctic have demonstrated increased rates of myopia among young Inuit adults indigenous to the region. We examined the refractive status of Yupik Eskimos, a group that had not previously been evaluated. Our subjects were young adults born between November 1960 and December 1962 to persons living in 10 villages in southwestern Alaska. The refractive status was obtained for 92% of these persons. The prevalence of myopia (refractive error -0.50 D or greater) was 68%, a rate among the highest reported for a general population anywhere in the world. The young women were significantly more myopic than the young men (mean refractive errors -1.91 and -1.36 D respectively). Astigmatism and myopia were positively correlated (r = 0.20, p less than 0.01). The etiology of myopia in this population is under study.

In 1981, a hepatitis B virus vaccine demonstration project was conducted in 1630 Yupik Eskimos in southwest Alaska. Levels of antibody to hepatitis B surface antigen and markers for hepatitis B virus infection in vaccinees were monitored yearly for 5 years. After 5 years of follow-up, 19% of those who initially had an immune response to vaccine of 10 sample ratio units or greater subsequently had levels of antibody to hepatitis B surface antigen lower than 10 sample ratio units. During the 5 years after the first dose of vaccine, in three responders and one person with an antibody to hepatitis B surface antigen response lower than 10 sample ratio units, antibody to hepatitis B core antigen developed, and the level of antibody to hepatitis B surface antigen was boosted. Hepatitis B surface antigen did not develop in any subjects, and none had clinical hepatitis. In the 5 years following the demonstration project, the annual incidence of hepatitis B virus infection decreased from 50 cases per 1000 population before the vaccine trial to 0.45 per 1000.

A 1960-62 study of southwestern Alaskan Eskimos documented an infant mortality rate--102.6 deaths per 1,000 live births--that was four times greater than that of U.S. whites. In 1980-81, 20 years after the original study, a similar cohort was identified in this population so that changes in infant mortality and other birth characteristics could be examined. Average birth weight and the amount of prenatal care received by the mothers increased from 1960 to 1980. Birth weight and prenatal visits were positively correlated. Results of the followup also revealed a 1980-81 infant mortality rate--17.1 deaths per 1,000 live births--that was less than a fifth of the 1960-62 rate and no longer significantly different from the national rate. Major changes associated with the decrease in mortality during the first 28 days of life (neonatal mortality) were a significant increase in the proportion of infants born in hospitals and an associated decrease in the number of deaths of infants weighing less than 2,500 grams at birth. The reduction in mortality during the rest of the first year of life was related to a decrease in deaths due to infectious diseases, particularly measles and pertussis. Changes in infant mortality reflect the increased availability of health care in this region, improved immunization programs, and the establishment of the Bethel Prematernal Home in Bethel, AK.

In 1981, a hepatitis B vaccine demonstration project was initiated among Yupik Eskimos of southwest Alaska to demonstrate that, under field conditions, the vaccine was safe, immunogenic, and efficacious. Laboratory tests for serologic markers of hepatitis B virus infection (HBsAg, anti-HBs, and anti-HBc) performed on sera collected in May 1981 from 3,988 residents of 17 remote Eskimo villages revealed that 2,645 (66.3%) had no evidence of hepatitis B virus infection. Because of a limited supply of vaccine, specific criteria for selection were used so that those at highest risk of infection would be immunized first. In November 1981, the first dose of vaccine was administered to 1,693 carefully selected individuals. The second dose was administered to 1,678 (99.1%) of those who received the first dose, and the final dose was administered to 1,630 persons (96.3%). Serologic follow-up showed the vaccine to be safe (0.4% experienced minor adverse reactions) and immunogenic (97.4% developed antibody). Vaccine-induced antibody levels were significantly higher for persons less than 30 years of age (p less than 0.001) and for females (p less than 0.001). Vaccine recipients were also protected from hepatitis B virus infection (p = 0.002). This public health measure proved to be feasible and effective in this remote arctic population despite difficult conditions for delivery and administration of this temperature-sensitive vaccine. This strategy for immunization is now being applied on a larger scale in Alaska as part of a program for the primary prevention of this infection and its sequelae.