José Luis Valdespino

Improvement of child survival in Mexico: the diagonal approach

Public health interventions aimed at children in Mexico have placed the country among the seven countries on track to achieve the goal of child mortality reduction by 2015. We analysed census data, mortality registries, the nominal registry of children, national nutrition surveys, and explored temporal association and biological plausibility to explain the reduction of child, infant, and neonatal mortality rates. During the past 25 years, child mortality rates declined from 64 to 23 per 1000 livebirths. A dramatic decline in diarrhoea mortality rates was recorded. Polio, diphtheria, and measles were eliminated. Nutritional status of children improved significantly for wasting, stunting, and underweight. A selection of highly cost-effective interventions bridging clinics and homes, what we called the diagonal approach, were central to this progress. Although a causal link to the reduction of child mortality was not possible to establish, we saw evidence of temporal association and biological plausibility to the high level of coverage of public health interventions, as well as significant association to the investments in women education, social protection, water, and sanitation. Leadership and continuity of public health policies, along with investments on institutions and human resources strengthening, were also among the reasons for these achievements.

Immunization of Six-Month-Old Infants with Different Doses of Edmonston–Zagreb and Schwarz Measles Vaccines

Because measles causes an estimated 2 million deaths per year among children in developing countries, including a substantial proportion of infants less than nine months old--the age at which vaccination is recommended--there has been interest in using different strains of vaccine and higher doses to achieve immunization of younger infants. We conducted a randomized trial of three different doses of Edmonston-Zagreb and of Schwarz measles vaccines in infants to evaluate the effect of the strain and dose of vaccine on the serologic response and acute adverse reactions to vaccination. Six-month-old infants received a standard, medium, or high dose of one of the vaccines, and nine-month-old infants received a standard dose. Antibody levels were measured before and after vaccination, by means of a plaque-reduction neutralization assay, in 1061 six-month-olds and 299 nine-month-olds. Edmonston-Zagreb vaccine produced higher rates of seroconversion and seropositivity than comparable doses of Schwarz vaccine. Among the six-month-old infants, the seroconversion rate 18 weeks after vaccination with the standard dose of Edmonston-Zagreb vaccine was 92 percent, that with the medium dose was 96 to 97 percent, and that with the high dose was 98 percent; the rates for the corresponding doses of Schwarz vaccine were 66 percent, 76 percent, and 91 percent, respectively. Higher seroconversion rates were observed with an increase in the dose of either Edmonston-Zagreb (P less than 0.01) or Schwarz (P less than 0.001) vaccine. The seroconversion rates produced by high and medium doses of Edmonston-Zagreb vaccine in six-month-olds were equal to or significantly higher than the rate produced by a standard dose of Schwarz vaccine in nine-month-olds (87 percent). Clinical adverse reactions were not associated with the strain or dose of a vaccine. We conclude that Edmonston-Zagreb vaccine is more immunogenic than Schwarz vaccine in infants and can induce effective immunization against measles at six months of age.

Seroepidemiología de la enfermedad de Chagas en México

The lack of information about Chagas disease in Mexico, as well as the controversy concerning its importance, was the basis for the seroprevalence study of Trypanosoma cruzi in the National Seroepidemiology Survey (NSS). This information was representative of the national situation with regard to disease prevalences and other factors related to the nations health. Unfortunately the NSS was not a very good information source for the study of trypanosomiasis americana, because its coverage in the disperse rural areas was poor. Nevertheless, the results of the NSS indicated that Chagas disease has an irregular distribution in Mexico with seroprevalences of 1.6, 0.5 and 0.2 for the different dilution levels used in the evaluation. The survey data showed Chagas disease to be less important than that mentioned by other authors. The NSS data confirmed the areas of disease transmission already reported and identified some new ones in Hidalgo, Chiapas and Veracruz. The survey also detected migratory workers with Chagas antibodies in Baja California border cities, a situation which indicates a risk for blood transfusion in areas of the country presumed to be free of the disease. Three quarters (74.5%) of the seropositive population were less than 39 years old. Moreover, the fact that children of less than four year were infected suggests that natural transmission is still very important in some areas. Although the seroprevalences were greater in the lower socio-economic groups, some persons of the higher socio-economic level were also affected. This situation may be explained by the fact that many of these persons own vacation homes in tropical areas.

Population-Based Prevalence of Symptomatic and Asymptomatic Astrovirus Infection in Rural Mayan Infants

Symptomatic and asymptomatic astrovirus infection was prospectively determined in a 3-year birth cohort of Mayan infants. Stool samples from 271 infants and 268 older siblings were tested for astrovirus, adenovirus 40/41, rotavirus and Salmonella, Shigella and Campylobacter species. Concurrent diarrhea, vomiting, fever, or anorexia were noted. Astrovirus was detected in 164 infants (61%) and 20 siblings (7%). Rotavirus (4%) and adenovirus 40/41 (13%) were isolated less frequently. Of all diarrheal episodes reported at a visit, 26% (78/305) were associated with astrovirus; 17% (78/452) of astrovirus infections were associated with diarrhea and 9% with other symptoms. Only diarrhea was associated with astrovirus infection (odds ratio, 1.4; 95% confidence interval [CI], 1.07-1.92; P = .01). Of infants with astrovirus, 70% shed at multiple visits over a period of 2-17 weeks (median, 5). The point prevalence of astrovirus infection was significantly higher among infants than siblings (relative risk, 6.18; 95% CI, 3.93-9.72; P < .0001, chi2). Astrovirus was identified throughout the year, peaked in March and May, and decreased in September. In this population, astrovirus was the most common enteric pathogen isolated; symptomatic infection was prevalent among infants.

Seroprevalencia de la hepatitis C en adultos de México: ¿un problema de salud pública emergente?

Objective. Hepatitis C Virus (HCV) infection is becoming a chronic disease in 60-85% of individuals and is a cause of hepatic cirrhosis and hepatocellular carcinoma. The objective of this study was to report the seroprevalence of HCV infection in a probabilistic sample of the Mexican population. Material and Methods. This study is based on information obtained from the National Health Survey conducted in 2000. A total of 21 271 sera randomly selected for anti-HCV and RNA of HCV was studied. It was performed at the National Institute of Public Health in 2005. Results. Seroprevalence of HCV antibodies was 1.4% (IC95% 1.1%-1.6%), of which 35.7% had active infection. Risk factors for infection were using heroine (RM= 9.8, IC: 2.1-41.4), being separated from his/her spouse (RM= 2.6, IC: 1.1-5.9), being a widower (RM= 2.2, IC: 1.1-4.3) and living in the northern states in the country (RM= 1.9, IC: 1.1-3.2). Conclusion. Results from this study indicate that HCV is an emerging public health problem in Mexico. Risk factors indicate that the main route of transmission is through transfusion of blood products (previous to 1996) and the second route is through usage of intravenous drugs and sexual practices.

Host and Viral Factors Affecting the Decreased Immunogenicity of Sabin Type 3 Vaccine after Administration of Trivalent Oral Polio Vaccine to Rural Mayan Children

Abstract Factors affecting immunogenicity of the first 2 doses of oral poliovirus vaccine (OPV) among unimmunized Mayan infants were prospectively evaluated. The relative impact of multiple variables, including mass or routine vaccination, concurrent enteric bacterial (salmonella, shigella, and campylobacter) and viral (adenovirus 40/41, astrovirus, nonpolio enteroviruses, and rotavirus) infections, interference among Sabin vaccine viruses, and preexisting poliovirus antibodies were studied. Sera were available from 181 infants after 2 OPV doses. Seroresponses were 86% to Sabin type 1, 97% to Sabin type 2, and 61% to Sabin type 3 vaccines. Mass versus routine vaccination and preexisting poliovirus antibodies did not affect immunogenicity. By multiple logistic regression analysis, fecal shedding of homologous Sabin strains was associated with increased seroresponses to all Sabin types, especially to Sabin type 3. Decreased OPV immunogenicity was primarily attributable to interference of Sabin type 3 by Sabin type 2. OPV formulations with higher doses of Sabin type 3 could improve immunogenicity among infants in developing countries.

Prevalencia en México de la infección y el estado de portador de la hepatitis B en adultos

Objective. To estimate the prevalence of chronic hepatitis B infection and carrier status in Mexico; to analyze the frequency and distribution of hepatitis B markers in relation to the demographic and geographic variables and to identify risk factors. Materials and Methods. A total of 12 014 sera samples from the 2000 National Health Survey that were randomly selected for Anti-HB c and HBsAg were studied. The sera were collected between November 1999 and June 2000 on a national level. Results. Seroprevalence for anti-HB c and HBsAg were 3.3% (CI 95%: 2.8-3.9) and 0.21% (0.11-0.37), respectively. Odds ratios adjusted by age for anti-HB c were: 15.3 for subjects 50 to 59 years old as compared with adults less than 29 years of age; 2.6 for residents in the southern region of the country as compared with residents in the central region; 4.6 for laborers as compared with business owners; 2.1 for women having had stillbirths; and 1.7 for adults having initiated sexual relations before 25 years of age. Conclusion. The epidemiological pattern for hepatitis B in Mexico is lower than the data worldwide. Nevertheless, it is of concern that 1.7 million Mexicans have suffered from the infection caused by this virus and 107 000 suffer from a chronic carrier status.

Seroepidemiología de la hepatitis A en México: Sensor de inequidad social e indicador de políticas de vacunación

Objective. Hepatitis A Virus (HAV) in Mexico has traditionally been considered a disease with a homogeneous pattern of transmission, high rates of infection at early ages, and infrequent complication rates. The purpose of this study was to take advantage of the 2000 NHS, a probabilistic population-based survey, in order to describe the seroepidemiology of HAV infection in Mexico. Material and Methods. This study is based on information obtained from the National Health Survey that was conducted in 2000. The present report is based on 4 907 randomly selected samples that were studied to determine the prevalence of HAV antibodies using immunoenzymatic assay. Sera were collected from November 1999 to June 2000. Results. Seroprevalence among the general population was 81.3% (CI95%: 78.684.2); expanded results allow the inference that 78.7 million Mexicans have been infected by this agent. Risk factors for HAV among children younger than nine years of age are the following: residence in southern states OR=5.3, residence in rural communities OR= 3.1, low-income family OR= 2.4 and living in households with limited access to sanitary facilities (water OR= 2.5 and sewage OR= 2.7). Conclusions. Results of this study demonstrate that HAV transmission patterns are heterogeneous and that differentials in the prevalence of infection are due to sanitary and social inequity among studied populations. Finally, the advantages of adopting public health measures such as vaccination and improvement of sanitary and socioeconomic conditions are discussed.

Diseño y metodología de la Encuesta Nacional de Salud 2000

OBJETIVO: Como parte del Sistema de Encuestas Nacionales de Salud, durante los ultimos meses de 1999 y los primeros tres del ano 2000 se realizo la Encuesta Nacional de Salud de Mexico (ENSA 2000). Se estudio la accesibilidad, calidad, utilizacion y cobertura de los Servicios de Salud; de modo adicional se actualizaron los marcadores serologicos de enfermedades infecciosas prevenibles por vacunacion, infecciones de transmision sexual y hepatitis. MATERIAL Y METODOS: Para la ENSA 2000 se seleccionaron tres grupos etarios y a los utilizadores de los servicios de salud. Se capto la informacion mediante entrevista directa y se tomaron muestras biologicas para analisis clinicos y medidas de parametros biologicos y somatometricos. El diseno muestral de la ENSA 2000 fue probabilistico, polietapico, estratificado y de conglomerados. El tamano de la muestra fue de 1 470 viviendas por estado, para un total de 47 040 viviendas a nivel nacional; los factores de expansion se modificaron por la falta de respuesta y la posestratificacion. El personal operativo se capacito y estandarizo para mantener una alta respuesta, en especial para las muestras de sangre. RESULTADOS: En total se obtuvieron 83 157 muestras de sangre de las 94 000 esperadas (respuesta de 88%) que se mantuvieron refrigeradas en tanto se ubicaron en el laboratorio del Instituto Nacional de Salud Publica donde se prepararon cuatro alicuotas y se congelaron a -150° C hasta el analisis.

Aumento de la sobrevida en menores de cinco años en México: la estrategia diagonal

Las intervenciones en salud publica dirigidas a ninos en Mexico han ubicado a este pais entre los siete paises encaminados a cumplir las metas de reduccion de la mortalidad infantil para 2015. La informacion para este estudio se ha tomado de diferentes fuentes: los censos poblacionales; los registros de mortalidad de la Secretaria de Salud y del Instituto Nacional de Estadistica, Geografia e Informatica; el registro nominal de ninos recolectado por el Programa de Vacunacion Universal; y las encuestas nacionales de nutricion. Con estos datos se estudio la asociacion temporal y la plausibilidad biologica de las diferentes intervenciones en salud publica, para explicar la reduccion de las tasas de mortalidad entre ninos, infantes y recien nacidos. Las tasas de mortalidad en menores de cinco anos han descendido de casi 64 muertes a menos de 23 por cada 1 000 ninos nacidos vivos registrados en los ultimos 25 anos. Se observo una reduccion drastica en las tasas de mortalidad por diarrea, junto con la eliminacion de polio, difteria y sarampion. El estado nutricional de los ninos mejoro de manera significativa en cuanto a bajo peso para la talla, baja talla para la edad y bajo peso para la edad. En los ultimos 25 anos, se mantuvieron intervenciones altamente costo-efectivas que acercaron los servicios de salud de atencion primaria a los hogares, lo que aqui se ha llamado estrategia diagonal. A pesar de que no es posible establecer una relacion de causalidad entre la reduccion de la mortalidad en menores de cinco anos y los factores investigados, se presenta evidencia basada en la asociacion temporal y en la plausibilidad biologica que indica que la alta cobertura de las intervenciones de salud publica, los avances en educacion de las mujeres, proteccion social, disponibilidad de agua potable y saneamiento, asi como nutricion, impactaron en el resultado observado. Por otro lado, el liderazgo y la continuidad de las politicas de salud publica junto con el reforzamiento de la infraestructura institucional tambien contribuyen a explicar la reduccion en las tasas de mortalidad en menores de cinco anos.