Browsing by Author "Vial, PA"

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    Age-specific prevalence of antibodies to hepatitis A in Santiago, Chile: Risk factors and shift in age of infection among children and young adults
    (2002) Fix, AD; San Martin, O; Gallicchio, L; Vial, PA; Lagos, R
    Transition from high to lower endemicity of hepatitis A virus (HAV) infection may portend increased public health burden with the shift of infection to older ages and increasing morbidity and mortality. This report describes age-specific prevalence of antibodies to HAV (anti-HAV) among children and young adults in Santiago, Chile, compared with previous prevalence data and assesses factors predictive for anti-HAV. In 1998, a serosurvey was performed in Metropolitan Santiago, designed to enroll a representative, age-stratified population on the basis of area of residence. A total of 784 individuals (age range, 1-24 years) were enrolled. Anti-HAV prevalence by year of life was as follows: ages 1 to 4,12.5%; 5 to 9, 26.2%; 10 to 14, 43.4%; 15 to 19, 57.4%; 20 to 24, 73.9%. Adjusting for age, factors associated (inversely) with anti-HAV included residential areas of higher socioeconomic status (SES), parental education, and household characteristics of potable water, municipal sewage system, and the presence of a toilet or refrigerator in the house. In logistic regression analysis, only maternal years of education and residence in areas of higher SES remained independently associated with anti-HAV. Excluding those from higher SES areas, comparison of the age-specific anti-HAV prevalence data from previous studies of similar methodology in areas of lower SES revealed consistent decreases across all age groups; the age-standardized prevalence for this age range (1-24 years) dropped from 53.7% in 1990 to 40.6% in 1998. In light of the growing pool of susceptible individuals at older ages, with HAV continuing to circulate in the communities, evaluation of the feasibility of vaccination programs would be judicious.
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    Efficacy of hepatitis A vaccination in children aged 12 to 24 months
    (2001) Abarca, K; Ibañez, I; Flores, J; Vial, PA; Safary, A; Potín, M
    Background. Current hepatitis A vaccines are either licensed for children >2 years of age. as in the U.S. or Chile, or >1 year of age, as in Europe and other parts of the world. Recent recommendations for immunization against hepatitis A have included routine vaccination of children in areas or regions of higher endemicity. However, data on hepatitis A vaccination in toddlers aged between 1 and 2 years are scarce.
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    Peridomestic small mammals associated with confirmed cases of human hantavirus disease in southcentral Chile
    (2004) Torres-Pérez, F; Navarrete-Droguett, J; Aldunate, R; Yates, TL; Mertz, GJ; Vial, PA; Ferrés, M; Marquet, PA; Palma, RE
    Cases of human hantavirus disease have been reported in Chile since 1995, most of them in people living in rural and periurban areas. We conducted a peridomestic study of small mammals to evaluate the relationships between the presence of rodents with antibodies to Andes virus confirmed human cases of hantavirus pulmonary syndrome in southcentral Chile. The results of 20 sampled sites, which involved the capture of 272 mice over an 18-month period, showed the occurrence of 10 small mammal species, of which Oligoryzomys longicaudatus was the only seropositive species for hantavirus, with an intra-specific serologic rate of 10.4%.
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    Seroprevalence of parvovirus B19 in urban Chilean children and young adults, 1990 and 1996
    (2002) Abarca, K; Cohen, BJ; Vial, PA
    An immunofluorescence test for detecting parvovirus B19 IgG was developed by infecting insect cells with recombinant baculovirus expressing the capsid protein VP1. The test was used to study the prevalence of antibodies in 725 healthy children and young adults living in Santiago, Chile. In total, 248 sera were taken in 1990 and 477 in 1996. The seroprevalence was low in children less than 5 years old (3 % in 1990 and 21 % in 1996). It rose during school age to a prevalence around 50 %, reaching 60 % in young adults. No differences were found between genders. There was a statistically significant higher seroprevalence in the low socioeconomic status group in 1990 samples, but this was not observed in 1996. The higher prevalence observed in children less than 5 years of age in 1996 compared with 1990 could be explained by the occurrence of intervening epidemics of parvovirus B19 infection.
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    Time course of antibody response to tetanus toxoid and pneumococcal capsular polysaccharides in patients infected with HIV
    (LIPPINCOTT WILLIAMS & WILKINS, 1998) Talesnik, E; Vial, PA; Labarca, J; Mendez, C; Soza, X
    The temporal course of the humoral immune response to T-cell-dependent and T-cell-independent type 2 antigens was evaluated in HIV-infected patients. In all, 26 seropositive patients were vaccinated with tetanus toroid and 23-valent pneumococcal vaccines; total IgG and IgG1 antibodies to tetanus toroid (Ttox) and total IgG and IgG2 antibodies against 23 Streptococcus pneumoniae capsular antigens (PPS) were measured at baseline, 2 months, and 12 months after vaccination. For the Ttox, baseline levels of IgG1 (Ttox-IgG1) increased from 11.0 to 19.5 mg/L at 2 months postimmunization. Overall only 6 patients (23%) showed a significant response. At 12 months postvaccination, Ttox-IgG and T-tox-IgG1 were significantly lower than baseline levels (Ttox IgG basal; 11.0 mg/L, 12 months; 0.8 mg/L, Ttox IgG1 baseline; 13.1 mg/L, Ttox IgG1 12 months; 2.4 mg/L) and in 10 patients, antibodies that fell below protective levels (0.6 mg/L). In contrast with PPS, a significant response was observed at 2 and 12 months (PPS-IgG basal; 35.9 U/ml, 2 months; 151.4 U/ml, 12 months; 59.7 U/ml; PPS-IgG2 baseline 20.3 U/ml, 2 months; 113.2 U/ml, 12 months; 51..9 U/ml). Overall, 19 patients (76%) showed an immune response to pneumococcal polysaccharides antigens. Immunization with the Ttox T-cell-dependent antigen fails to elicit a significant immune response and may induce inhibition of antibody production in HIV-infected patients. In contrast, immunization with a T-cell-independent type 2 antigen can cause the pneumococcal polysaccharides to induce significant immune response in a high proportion of HIV-infected patients.