Seroprevalence of human parvovirus B19 in a suburban population in São Paulo, Brazil

OBJETIVO: Analisar a prevalência de anticorpos IgG ao parvovírus humano B19. MÉTODOS: Estudo transversal em uma comunidade de subúrbio de São Paulo, Brasil, de novembro 1990 a janeiro de 1991. Amostras aleatórias (N=435) e representativas de soro foram coletadas de crianças sadias a partir de 15 dias de idade e de adultos com até 40 anos. Os anticorpos IgG ao parvovírus humano B19 foram detectados pelo teste ELISA. RESULTADOS: A prevalência de anticorpos IgG ao parvovírus B19 foi de 87 por cento dos recém-nascidos. A prevalência de anticorpos IgG de origem materna decaiu exponencialmente até o 19o mês de idade. Baixa prevalência de anticorpos foi observada nos primeiros quatro anos de vida, aumentando até 72 por cento no grupo etário de 31-40 anos. A idade média de aquisição da primeira infecção nesta comunidade é de 21 ± 7 anos. A idade ótima para se vacinar as crianças desta comunidade com uma vacina hipotética é de um ano de idade. CONCLUSÕES: A prevalência de anticorpos IgG ao parvovírus B19 foi alta entre recém-nascidos e no grupo etário 31-40 anos. A análise por estrutura etária mostrou padrão similar aos estudos prévios relacionados à baixa prevalência de infecção em crianças que aumenta com a idade.

Seroprevalence of human parvovirus B19 in a suburban population in São Paulo, Brazil.

OBJECTIVE: To analyze the prevalence of IgG antibodies to human parvovirus B19. METHODS: Cross-sectional study in a suburban community in São Paulo, Southeastern Brazil, between November 1990 and January 1991. Randomly selected (N=435) representative samples of sera were collected from healthy children older than 15 days old and adults up to 40 years old. IgG antibodies were detected using ELISA. RESULTS: High prevalence of IgG antibodies to B19 parvovirus was found in 87% of newborns. The prevalence of maternally derived IgG antibodies exponentially plunged up to the 19th month of age. Low prevalence of antibodies was found in the first 4 years of life, increasing up to 72% in those aged 31-40 years. It was estimated that the average age of first infection in this population is 21 +/- 7 years old and the optimal age for vaccination with a hypothetical vaccine would be 1 year of age. CONCLUSIONS: Parvovirus B19 IgG antibody prevalence was high in newborns and those aged 31-40 years. The analysis by age groups showed a pattern similar to that found in previous studies, i.e., low prevalence of infection in children that increases with age.

Population biology, evolution, and immunology of vaccination and vaccination programs.

The purpose of prophylactic vaccination is to reduce morbidity and mortality in a population. Many questions related to the design of vaccines and vaccination programs require a population standpoint for their sharp formulation and laboratory and field studies to understand their immunologic background. Practical suggestions of the workshop included increased studies of age-specific immunity, better immunoepidemiologic surveillance, better design of efficacy studies, and more systematic sampling of parasite strains to study the evolutionary pressure exerted by vaccines. Theoretical immunology has much to contribute. One of the realizations of the workshop was the value of a strong interdisciplinary approach in vaccine development, utilizing relevant contributions from immunology, population biology, mathematical modeling, epidemiology, molecular biology, and virology.

Acquired immunity to Africanized honeybee (Apis mellifera) venom in Brazilian beekeepers.

Seventy-eight Brazilian beekeepers who had been stung on average six times per month were studied. Sixty-eight beekeepers (87.1%) showed restricted local clinical reactions; nine individuals (11.5%) had extensive local reactions, and only one (1.2%) suffered anaphylactic shock. The humoral immunologic pattern of these individuals were studied by using immunoenzymatic methods to determine the serum titles of specific IgE and specific IgG4. Three groups of beekeepers presenting different humoral immunologic patterns were identified, in which the predominant pattern was the absence of specific IgE and high levels of specific IgG4 (38.4%). There was a positive correlation between the high levels of specific IgG4 and the number of bee stings. This correlation was not found in either specific or total IgE. The results of the present study suggest: i) the immunologic response to the number of exposures to Africanized honey-bee venom is not related to the number of exposures; and, ii) other nonhumoral and/or nonimmunologic factors may be involved in the reaction to the insect sting, which are responsible for both the clinical symptoms and protection.

Assessing the efficacy of a mixed vaccination strategy against rubella in São Paulo, Brazil.

BACKGROUND: In 1992 a major vaccination strategy against measles-mumps-rubella was introduced in the State of Saão Paulo, Brazil. This strategy was based on mathematical models and comprised a pulse vaccination covering all children aged 1-10 years, followed by the inclusion of this vaccine in the routine calendar at 15 months of age. The present work reports the evaluation of the efficacy of this mixed vaccination strategy. METHODS: A rubella seroprevalence survey was carried out immediately and one year after the campaign, comprising 4953 children aged 1-15 years. RESULTS: We show that average rubella seroprevalence increased from 0.40 to 0.97 and that the reported number of congenital rubella syndrome (CRS) cases dropped dramatically. CONCLUSIONS: The mixed vaccination strategy adopted against rubella has proved to be very effective in reducing the number of CRS cases in São Paulo.

Salivary antibody detection in epidemiological surveys: a pilot study after a mass vaccination campaign against rubella in São Paulo, Brazil.

The sensitivity and specificity of salivary rubella antibody detection was investigated using samples collected from 301 children after a mass vaccination campaign in the state of São Paulo, Brazil. Saliva samples were collected by 2 different methods: directly dribbling into a container or using a commercial collecting device. Corresponding finger-prick blood samples were collected on filter paper. Rubella specific immunoglobulin G (IgG) was measured in saliva by antibody capture radioimmunoassay and in blood samples by indirect enzyme-linked immunosorbent assay. The detection of salivary rubella specific IgG showed good correlation with the detection of rubella antibody in the blood samples. For both collecting techniques the predictive value for a positive saliva test was > 99% compared with the results from the blood tests. However, the predictive value for a negative saliva test was only 58.3% for a dribbled sample, compared to 100% for saliva collected using the commercial device. Moreover, collecting saliva by dribbling from children less than 4 years old was difficult. The detection of rubella specific IgG in saliva collected using a commercial device proved to be sensitive and specific in this epidemiological study, encouraging its more widespread application as a means of surveillance after mass vaccination.

Rubella seroepidemiology in a non-immunized population of São Paulo State, Brazil.

A rubella serological survey of 476 individuals selected by cluster sampling technique from Caieiras, a small town located in the outskirts of São Paulo city, southeastern Brazil, was carried out over the period November 1990-January 1991. The aim of the study was to characterize rubella epidemiology in a representative non-immunized community in south east Brazil. The survey comprised a seroprevalence study, stratified by age (0-40 years) and a seroconversion study of rubella vaccine in non-infected children below 2 years of age. Mathematical techniques were applied to resultant data sets to determine the age dependent rates of decay in the proportion of individuals with maternally derived antibodies, vaccine seroconversion, and infection of susceptibles, termed the force of infection, and to estimate the average age at first infection.

A model-based design of a vaccination strategy against rubella in a non-immunized community of São Paulo State, Brazil.

A mixed vaccination strategy against rubella is proposed. We describe how the vaccination strategy was designed with the help of mathematical techniques. The strategy was designed for application in a non-immunized community of the State of São Paulo, Brazil, and was implemented by local health authorities in 1992. This strategy comprises a pulse vaccination campaign, covering the age interval between 1 and 10 years, followed by the introduction of the vaccine in the immunization calendar at 15 months of age. The expected impact of the proposed strategy is discussed.

Effects of vaccination programmes on transmission rates of infections and related threshold conditions for control.

This study addresses the problem of the existence of conditions for persistence or eradication of age-dependent directly transmitted infections. The usual system of differential equations describing the dynamics of the disease is transformed into integral equations. The authors show how to solve these equations and, by applying the contraction mapping theorem, give conditions for the persistence or eradication of the infection. A practical illustration of the application of the methods proposed is sketched, using data for rubella collected from a small Brazilian community.

[Positive serology of syphilis, toxoplasmosis and Chagas' disease in pregnant women in their first visit to health centers in a metropolitan area, Brazil]. / Sorologia positiva para sífilis, toxoplasmose e doença de Chagas em gestantes de primeira consulta em centros de saúde de area metropolitana, Brasil.

The diagnosis of some infectious diseases contracted during pregnancy is very important, as these diseases can be transmitted to the fetus. Four hundred and eighty-one pregnant women were studied, of an average 24.5 years of age (from 14 to 46), during their first prenatal visit to the State of S. Paulo's Health Care Centres in the subdistrict of Paz (Butantan), City of S. Paulo, Brazil, between April and October, 1988. Classified by trimester of pregnancy, 230 patients (47.8%) fell into the first, 203 (42.2%) into the second and 48 (10%) into the third trimester. Of the 474 patients that declared their income, 309 (65.2%) earned 1 MSPC (minimum salary per capita) per month, which gives some indication of the low socioeconomic status of our patients is. The serologic tests for syphilis, toxoplasmosis and Chagas' disease were analysed for each patient, more than one technique being used for each. The results were as follows: 25 patients (5.2%) had a positive test for syphilis; in 67 patients (13.9%) active toxoplasmosis was diagnosed (Presence of IgM antibodies in 6); 14 patients (2.9%) were positive for Chagas' disease, among which 10 (71.4%) came from the States of Bahia and Minas Gerais, where this disease has a high prevalence.