Prevention and control of neoplasms associated with HPV in high-risk groups in Mexico City: The Condesa Study / Prevención y control de neoplasias asociadas a VPH en grupos de alto riesgo de la Ciudad de México: el Estudio Condesa

Abstract: Objective: To evaluate the effectiveness of a combined strategy of human papillomavirus virus (HPV) vaccination and high-risk HPV screening to reduce the occurrence of anogenital and oropharyngeal neoplasms among men who have sex with men, people with HIV, homeless people, transgender women, female sex workers and rape victims. Materials and methods: This mixed methods study evaluates the effectiveness of a combined vaccination-screening strategy to reduce HPV prevalence/incidence and occurrence of cervical intraepithelial neoplasms grade 2+ and/or anal intraepithelial neoplasms grade 2+, using Kaplan-Meier. The time-to-event method will evaluate time from positive results for specific anogenital HPV to incidence of anogenital lesions containing that HPV type. Results: People vaccinated against HPV and screened for HPV as a primary test will have lower prevalence and incidence of HPV infection and consequently lower frequency of HPV-related anogenital and oropharyngeal lesions. Conclusions: This study will generate scientific evidence on effectiveness of a combined vaccination-screening strategy to reduce the burden of HPV-associated neoplasms.

Resumen: Objetivo: Evaluar la efectividad de una estrategia combinada de vacunación contra el virus de papiloma humano (VPH) y tamizaje de VPH de alto riesgo para reducir neoplasias anogenitales y orofaringeas entre hombres que tienen sexo con hombres, personas con VIH, personas en situación de calle, mujeres transgénero, trabajadoras sexuales y víctimas de violación. Material y métodos: Este estudio evaluará la efectividad de una estrategia combinada de vacunación y tamizaje para reducir la ocurrencia de neoplasias intraepiteliales cervicales grado 2+ o neoplasias intraepiteliales anales grado NIA2+ utilizando Kaplan-Meier. Se evaluará tiempo de resultados positivos para tipos específicos de VPH anogenital a incidencia de lesiones anogenitales con ese tipo de VPH. Resultados: Las personas vacunadas contra VPH y con tamizaje de VPH tendrán menor prevalencia e incidencia de infecciones por VPH y por ende menor frecuencia de lesiones anogenitales y orofaringeas relacionadas con VPH. Conclusiones: Este estudio generará evidencia científica sobre la efectividad de una estrategia combinada de vacunación y tamizaje para reducir la carga de neoplasias asociadas al VPH.

Prevention and control of neoplasms associated with HPV in high-risk groups in Mexico City: The Condesa Study.

OBJECTIVE: To evaluate the effectiveness of a combined strategy of human papillomavirus virus (HPV) vaccination and high-risk HPV screening to reduce the occurrence of anogenital and oropharyngeal neoplasms among men who have sex with men, people with HIV, homeless people, transgender women, female sex workers and rape victims. MATERIALS AND METHODS: This mixed methods study evaluates the effectiveness of a combined vaccination-screening strategy to reduce HPV prevalence/incidence and occurrence of cervical intraepithelial neoplasms grade 2+ and/or anal intraepithelial neoplasms grade 2+, using Kaplan-Meier. The time-to-event method will evaluate time from positive results for specific anogenital HPV to incidence of anogenital lesions containing that HPV type. RESULTS: People vaccinated against HPV and screened for HPV as a primary test will have lower prevalence and incidence of HPV infection and consequently lower frequency of HPV-related anogenital and oropharyngeal lesions. CONCLUSIONS: Thisstudy will generate scientific evidence on effectiveness of a combined vaccination-screening strategy to reduce the burden of HPV-associated neoplasms.

OBJETIVO: Evaluar la efectividad de una estrategia combinada de vacunación contra el virus de papiloma humano (VPH) y tamizaje de VPH de alto riesgo para reducir neoplasias anogenitales y orofaringeas entre hombres que tienen sexo con hombres, personas con VIH, personas en situación de calle, mujeres transgénero, trabajadoras sexuales y víctimas de violación. MATERIAL Y MÉTODOS: Este estudio evaluará la efectividad de una estrategia combinada de vacunación y tamizaje para reducir la ocurrencia de neoplasias intraepiteliales cervicales grado 2+ o neoplasias intraepiteliales anales grado NIA2+ utilizando Kaplan-Meier. Se evaluará tiempo de resultados positivos para tipos específicos deVPH anogenital a incidencia de lesiones anogenitales con ese tipo de VPH. RESULTADOS: Las personas vacunadas contra VPH y con tamizaje de VPH tendrán menor prevalencia e incidencia de infecciones por VPH y por ende menor frecuencia de lesiones anogenitales y orofaringeas relacionadas con VPH. CONCLUSIONES: Este estudio generará evidencia científica sobre la efectividad de una estrategia combinada de vacunación y tamizaje para reducir la carga de neoplasias asociadas al VPH.

[Decrease of HCV seroprevalence in Mexico: Results from the National Health and Nutrition Survey 2012]. / Disminución de la seroprevalencia de hepatitis C en México: resultados de la Ensanut 2012.

OBJECTIVE: To estimate seroprevalence of hepatitis C virus (HCV) among 15-49 years old Mexicans living in households and to describe the profile of seroreactive individuals. MATERIALS AND METHODS: Cross-sectional study implemented in 2012 using a national probabilistic sample with behavioral data from face-to-face interviews at households and HCV antibodies screening using capillary blood from same individuals. RESULTS: HCV seroprevalence in Mexico was estimated at 0.27% (IC95% 0.12-0.60), representing 161 000 persons. Seroprevalence was significantly higher among males (0.45% CI95% 0.01-0.89) than females (0.10% CI95% 0.00-0.22). Multivariate analysis suggests a higher possibility of HCV reactivity among men, increasing with age and higher among those sexually active, and lower for higher socioeconomic level. CONCLUSION: HCV seroprevalence in Mexico by 2012 seems significantly lower than the estimation from 2000 of 1.2% for the same age-group. Evidence of infection among individuals 15-19 years old suggests the need to strength preventive actions, particularly in subjects with risky behaviors.

Disminución de la seroprevalencia de hepatitis C en México: resultados de la Ensanut 2012 / Decrease of HCV seroprevalence in Mexico: Results from the National Health and Nutrition Survey 2012

Objetivo. Estimar la seroprevalencia del virus de la hepatitis C (VHC) en población mexicana en viviendas particulares y explorar aspectos del perfil poblacional de serorreactividad. Material y métodos. Estudio transversal con una muestra probabilística de la población del país entre 15 y 49 años en el año 2012, con información sociodemográfica obtenida por entrevista en los hogares y determinación de anticuerpos al VHC por inmunoensayo de micropartículas en sangre capilar. Resultados. La seroprevalencia de VHC en México se estimó en 0.27% (IC95% 0.12-0.60), equivalente a 161 000 personas en el país, y fue mayor entre hombres (0.45% IC95% 0.01-0.89) en comparación con mujeres (0.10% IC95% 0.00-0.22). El análisis multivariado señala que la posibilidad de un resultado positivo a VHC es mayor entre hombres, aumenta con la edad y entre los sexualmente activos, y es menor en la población de mayor nivel socioeconómico. Conclusiones. La seroprevalencia observada de VHC resulta significativamente menor que la estimada en el año 2000 (1.2%) para el mismo grupo de edad. La evidencia de casos entre individuos de 15 a 19 años sugiere la necesidad de fortalecer acciones preventivas recomendadas internacionalmente, con énfasis en la población expuesta al VHC por prácticas de riesgo.

Objective. To estimate seroprevalence of hepatitis C virus (HCV) among 15-49 years old Mexicans living in households and to describe the profile of seroreactive individuals. Materials and methods. Cross-sectional study implemented in 2012 using a national probabilistic sample with behavioral data from face-to-face interviews at households and HCV antibodies screening using capillary blood from same individuals. Results. HCV seroprevalence in Mexico was estimated at 0.27% (IC95% 0.12-0.60), representing 161 000 persons. Seroprevalence was significantly higher among males (0.45% CI95% 0.01-0.89) than females (0.10% CI95% 0.00-0.22). Multivariate analysis suggests a higher possibility of HCV reactivity among men, increasing with age and higher among those sexually active, and lower for higher socioeconomic level. Conclusion. HCV seroprevalence in Mexico by 2012 seems significantly lower than the estimation from 2000 of 1.2% for the same age-group. Evidence of infection among individuals 15-19 years old suggests the need to strength preventive actions, particularly in subjects with risky behaviors.

Seroprevalencia de VIH en población mexicana de entre 15 y 49 años: resultados de la Ensanut 2012 / HIV seroprevalence among Mexicans age 15 to 49: results from the National Health & Nutrition Survey 2012

Objetivo. Estimar la seroprevalencia de VIH en población mexicana no institucionalizada de 15 a 49 años, y aspectos selectos del perfil de la población serorreactiva. Material y métodos. Estudio transversal con una muestra probabilística de la población del país de 15 a 49 años, con información sobre comportamientos obtenida por entrevista directa en los hogares y determinación de anticuerpos para VIH en sangre capilar. Resultados. Se identificó una seroprevalencia de 0.15% (IC95% 0.09-0.21) en la población de 15 a 49 años; de 0.07% (IC95% 0.03-0.11) en mujeres, y de 0.24% (IC95% 0.11-0.36) en hombres. La población serorreactiva a VIH son hombres jóvenes, de mayor nivel socioeconómico en relación con la población general y con información que sugiere una mayor cobertura por la seguridad social (49.9% en serorreactivos contra 34.5% en no serorreactivos). El 49.4% de los serorreactivos contra 18.5% de los no serorreactivos se había realizado al menos una prueba de detección de VIH. Conclusiones. La seroprevalencia de VIH estimada en la Encuesta Nacional de Salud y Nutrición (Ensanut) 2012 sugiere que ésta se ha mantenido relativamente estable desde 2000. La estimación representa alrededor de 104000 personas (rango de entre 53000 y 126000) de 15 a 49 años que viven con VIH en México (75% de los cuales son hombres), de los que 50.6% desconocería su estatus serológico. Implementando un modelo de corrección de sesgo y agregando a los estimados en hogar, los casos estimados entre población de hombres que tienen sexo con hombres (tanto homosexual como bisexual), la estimación de la seroprevalencia alcanzaría 0.23%, con un total de 140000 personas de 15 a 49 años viviendo con VIH (con un intervalo estimado de entre 92000 y 201000 personas).

Objective. To estimate the HIV seroprevalence among Mexicans aged 15 to 49 years old and living in households, and to describe the profile of serorreactive individuals. Materials and methods. Cross-sectional study with a national probabilistic sample of individuals aged 15 to 49 years with behavioral data from direct interview (face-to-face) at households and HIV screening using capillary blood collected from the same individuals. Results. A seroprevalence of 0.15% (95%CI 0.09-0.21) was estimated for Mexicans aged 15 to 49; seroprevalence among women was 0.07% (95%CI 0.03-0.11) and 0.24% (95%CI 0.11-0.36) for men. HIV serorreactive population is composed of younger men, with a higher socioeconomic level compared to the general population, and with a higher insurance coverage-social protection on health in general and social security in particular. Only 50% of the serorreactive individuals may be aware of their status as living with HIV. Conclusions. The estimated HIV seroprevalence in the NHNS 2012 suggests a stable pattern since 2000. The estimated prevalence among individuals 15 to 49 years was adjusted both for selection bias correction and to include MSM estimations (under the assumption that MSM is a population hard to reach in a household survey), resulting in a total seroprevalence of 0.23% and an estimated number of people with HIV of 140000.

[HIV seroprevalence among Mexicans age 15 to 49: results from the National Health & Nutrition Survey 2012]. / Seroprevalencia de VIH en población mexicana de entre 15 y 49 años: resultados de la Ensanut 2012.

OBJECTIVE: To estimate the HIV seroprevalence among Mexicans aged 15 to 49 years old and living in households, and to describe the profile of serorreactive individuals. MATERIALS AND METHODS: Cross-sectional study with a national probabilistic sample of individuals aged 15 to 49 years with behavioral data from direct interview (face-to-face) at households and HIV screening using capillary blood collected from the same individuals. RESULTS: A seroprevalence of 0.15% (95%CI 0.09-0.21) was estimated for Mexicans aged 15 to 49; seroprevalence among women was 0.07% (95%CI 0.03-0.11) and 0.24% (95%CI 0.11-0.36) for men. HIV serorreactive population is composed of younger men, with a higher socioeconomic level compared to the general population, and with a higher insurance coverage-social protection on health in general and social security in particular. Only 50% of the serorreactive individuals may be aware of their status as living with HIV. CONCLUSIONS: The estimated HIV seroprevalence in the NHNS 2012 suggests a stable pattern since 2000. The estimated prevalence among individuals 15 to 49 years was adjusted both for selection bias correction and to include MSM estimations (under the assumption that MSM is a population hard to reach in a household survey), resulting in a total seroprevalence of 0.23% and an estimated number of people with HIV of 140,000.

[Knowledge about herpes simplex virus type 2 and human papillomavirus, and risk perception to acquire infections among college students]. / Conocimiento sobre el virus herpes simple tipo 2 y virus del papiloma humano, y percepción de riesgo a adquirir las infecciones entre estudiantes universitarios.

INTRODUCTION: herpes simplex virus type 2 (HSV-2) and human papillomavirus (HPV) are the most frequent sexually transmitted infections (STI) among college students 18-24 years old. Educational interventions for STI prevention can help to decrease viral STI prevalence among students. OBJECTIVE: to know the change in knowledge, perception of risk and sexual behavior among 182 students of the Autonomous University of the State of Morelos. MATERIAL AND METHOD: a community intervention trial (before-after) was carried out, using brochures for prevention of HSV-2 and HPV, including information about these STI, with emphasis on the risk factors identified in students of the same university. RESULTS: we found a change in the perception of STI risk during the intervention (56.5 before vs. 67.7% after intervention), possibly the brochures assisted students to learn more about their own risk behaviors. Likewise, there was an increase in knowledge in both HPV and HSV-2. CONCLUSIONS: it is necessary to increase the sample size in future interventions to assess further the change in knowledge, sexual behaviors and the prevalence of infections.

Seroprevalence of hepatitis A virus in a cross-sectional study in Mexico: Implications for hepatitis A vaccination.

Hepatitis A virus (HAV) remains a public health concern worldwide contributing to significant morbidity in developed and developing countries. This cross-sectional database study estimated the overall HAV seroprevalence and the seroprevalence by gender, age, region and socioeconomic status in Mexico. Between January and October 2010, serum samples collected during the National Health and Nutrition survey (ENSANUT 2006) were obtained from subjects aged 1-95 y. Subjects' gender, age, geographical region and socioeconomic status were extracted from the survey and compiled into a subset database by the Mexican National Institute of Public Health. Anti-HAV antibodies were measured using a chemiluminescent immunoassay. A total of 3658 subjects were included in the according-to-protocol cohort. Overall, the HAV seroprevalence was 84.2%. The HAV seroprevalence rates were similar between females (86.1%) and males (82.2%). The percentage of subjects seropositive for anti-HAV antibodies was highest in adults aged ≥ 20 y (96.9%), followed by adolescents aged 10-19 y (80.1%) and lowest in children aged 1-9 y (45.0%) (p < 0.0001). Regionally, the highest HAV seroprevalence rate was observed in the South (88.8%) followed by Central and Northern Mexico and Mexico City (p = 0.02). The HAV seroprevalence was similar between subjects of high socioeconomic (90.1%) status and of low socioeconomic status (86.6%). This study confirms the intermediate HAV endemicity in Mexico. Cost-effectiveness studies are necessary to evaluate the inclusion of an effective hepatitis A vaccine from a population-based perspective in addition to continuous efforts to improve hygiene and sanitation that have a substantial impact on the disease burden.

Maternal/child seroprevalence of antibodies against Treponema pallidum at four general hospitals in the state of Morelos, Mexico.

BACKGROUND AND AIMS: Treponema pallidum can cause syphilis in pregnant women and congenital syphilis in the newborn. In Latin America, 330,000 pregnant women are diagnosed with syphilis every year. Adequate prenatal care to detect syphilis reduces maternal morbidity and fetal and neonatal mortality and morbidity. We undertook this study to determine T. pallidum seroprevalence among pregnant and puerperal women from Morelos, Mexico, as well as to evaluate the sexual behavior, demographic and clinical variables associated with the infection. METHODS: A cross-sectional study was carried out among pregnant and puerperal women from four general hospitals from Morelos, Mexico during 2005-2009. Women answered a questionnaire and provided a blood sample to detect antibodies against T. pallidum. RESULTS: A total of 2331 women were analyzed with 0.26% of T. pallidum seroprevalence. There were four cases with active syphilis and two cases with latent syphilis, as well as two cases of congenital syphilis. Illiterate women had 6.7 times higher risk of being infected. Women who did not undergo a urine test had a 5.3 times higher risk for infection and women who do not have piped water inside their household had a 5.0-fold higher risk of having anti-T. pallidum antibodies. All seropositive cases were from the same hospital (Cuautla General Hospital) with demographic, sexual behavior and medical care characteristics different from the other three hospitals. CONCLUSIONS: Syphilis during pregnancy and congenital syphilis are still present in Mexico. It may be that the more urban a population the higher the chance of the prevalence of maternal syphilis. It would be beneficial to reinforce the observance of the Official Mexican Norm and to implement rapid diagnostics tests to contend with this public health problem.

[Guideline for interpretation and report of the antibody to hepatitis C virus. Grupo de Desarrollo de la Guía ]. / Guía de interpretación y reporte del anticuerpo a hepatitis C.

Patients with hepatitis C virus (HCV) infection are detected by testing for the presence of antibodies to HCV (Anti-HCV). A positive Anti-HCV test represents a true positive result only in a variable proportion of subjects (35 to 95%). The qualitative interpretation as positive or negative Anti-HCV report is associated with a general lack of understanding regarding the interpretation of results, when more specific testing should be performed, and which tests should be considered for this purpose. Therefore, a substantial variation in supplemental testing practices exists among laboratories and physicians. This guideline was developed on the basis of the best available evidence to classify positive antibody in two (low and high) or three levels (very low, low and high) according to the signal to cutoff (S/CO) ratio: the very low level of the Anti-HCV identifies false-positive results and further diagnostic testing is not necessary. The low antibody level is frequently related with false-positive results and testing with Immunoblot is recommended; only Immunoblot-positive subjects require HCV RNA testing because of a low possibility of being viremic. The high Anti-HCV level is an accurate serological marker for predicting viremia and denotes the need of routine HCV RNA testing in order to efficiently confirm hepatitis C. Cost-effectiveness analysis, based on the Anti-HCV level, recommends the use of the two or three-levels to choose the confirmatory test of positive antibody. This approach can be implemented without increasing test costs because the S/CO ratio is automatically generated in most laboratory analyzers and would provide health care professionals with useful information for counseling and evaluating patients, to eliminate unwarranted notifications in cases of false antibody reactivity, and correctly identifying those Anti-HCV-positive patients who are infected and need antiviral treatment. The written report should include the antibody level (S/CO ratio), the type of the immunoassay applied and interpretation guideline. Anti-HCV testing is performed in multiple settings including blood banks or health department facilities; adoption of this Guideline for interpretation and report of the antibody to hepatitis C virus by laboratories and its implementation by clinicians will improve the accuracy for interpreting antibody result to determine the next step on hepatitis C diagnosis.

Heterogeneous distribution of hepatitis B serological markers in rural areas of Mexico.

OBJECTIVE: To study the distribution of the hepatitis B antibody (anti-HBc) based on a national serosurvey from 10 Mexican states showing a mean HBV prevalence higher than the national one. MATERIALS AND METHODS: This was a cross-sectional study. During 2003, anti-HBc was analyzed at INSP in 19 907 sera, and the related sociodemographic factors were determined. RESULTS: Anti-HBc prevalence was greater among men, but it was also associated to age, residence in a rural area, low socio-economic status, and illiteracy. Clusters of very high anti-HBc prevalence were found in several rural communities where the prevalence of anti-HBc in adults is 3 to 20 times the national average. CONCLUSIONS: Besides a low endemicity of HBV in Mexico, distribution is heterogeneous as was shown in several of the states studied, where there are rural towns with very high prevalence of HBV markers. National serosurveys are useful tools for identifying communities with hepatitis B hyperendemicity, where focused research and control measures are needed.

[Serological markers of hepatitis B and C, and HIV in La Calera and Cuambio, Guerrero, México]. / Marcadores serológicos de hepatitis B y C, y VIH en La Calera y Cuambio, Guerrero, México.

OBJECTIVE: To perform a hepatitis B, C, and HIV survey in an enhanced sample from two rural communities with the highest anti-HBc prevalence found in ENSA 2000. MATERIALS AND METHODS: This was a cross-sectional study.We studied the communities of La Calera and Cuambio, two adjacent rural towns of the district of Zirándaro, Guerrero, targeted because of the high prevalence of anti-HBc shown in ENSA 2000.We assessed the prevalence of hepatitis B and C, and HIV serological markers and associated factors among inhabitants older than 10 years. RESULTS: A very high prevalence of hepatitis B markers associated with socioeconomic factors was confirmed, while hepatitis C prevalence was low and HIV absent in the two communities addressed. CONCLUSIONS: National serosurveys are an accurate tool for identifying communities with hepatitis B high endemicity where focused research and control measures are needed.

Hepatitis C seroprevalence and correlation between viral load and viral genotype among primary care clients in Mexico.

OBJECTIVE: To measure hepatitis C virus (HCV) sero-prevalence, prevalence, hepatitis risk characteristics frequency, and genotype correlation with viral load among clients attending health care clinics. MATERIAL AND METHODS: Venous blood samples from l12 226 consecutive consenting adults were collected from January 2006 through December 2009. HCV antibodies were detected by immunoassay. HCV RNA was detected by qRT-PCR and viral genotype was performed by PCR and LIPA test. RESULTS: The HCV seroprevalence observed was l.5 % (C.I. 95% l.3-l.7), from seropositive individuals 60.9 % reported previous blood transfusion, 28.3% declared to have relatives with cirrhosis, 25.2% had tattoos or piercings, and 6.9% referred to have used drugs. Male gender and transfusion (p<0.001) were the most frequent hepatitis risk characteristics in the HCV seropositive group. Among seropositive subjects 48.3% presented HCV RNA.The most frequent genotype detected in all geographic areas of Mexico was l (subtype lA, 33%; subtype lB, 21.4%) followed by genotype 2 (subtype 2A, 8.50%). Subjects with genotype 1 had a significant correlation with the highest viral load. CONCLUSIONS: Our results show that nearly half of seropositive individuals are chronically infected. HCV infection has been shown in this study to be an emerging health problem in Mexico.

[Consensus on the clinical and microbiologic diagnosis of Bordetella pertussis, and infection prevention. Expert Group on Pertussis Vaccination]. / Consenso para el diagnóstico clínico y microbiológico y la prevención de la infección por Bordetella pertussis. Grupo de expertos en vacunación contra tos ferina.

Pertussis continues to be responsible for a significant disease burden worldwide. Although immunization practices have reduced the occurrence of the disease among children, waning vaccine- and infection-induced immunity still allows the disease to affect adolescents and adults who, in turn, can transmit the disease to non-immunized or partially immunized infants. This document is the result of a meeting in Mexico City of international experts who analyzed recent medical information in order to establish the current status of the epidemiology, diagnosis and surveillance of pertussis and, especially, the value of the dTpa booster dose in adolescents and adults as a pertussis prevention strategy in Mexico.

Consenso para el diagnóstico clínico y microbiológico y la prevención de la infección por Bordetella pertussis / Consensus on the clinical and microbiologic diagnosis of Bordetella pertussis, and infection prevention

La tos ferina sigue siendo responsable de una carga de enfermedad importante en el mundo. Aunque la implementación del uso de la vacuna contra esta enfermedad ha disminuido en gran medida el número de casos en la población pediátrica, se ha observado que la inmunidad inducida por la vacuna y por la infeccion natural disminuye con el tiempo lo que hace nuevamente susceptibles a adolescentes y adultos jóvenes que pueden transmitir la enfermedad a lactantes no inmunizados o con esquema de vacunación incompleto. Este documento, resultado de la reunión de un grupo internacional de expertos en la Ciudad de México, ha analizado la información médica reciente para establecer el estado actual de la epidemiología, diagnóstico, vigilancia y, especialmente, el valor de la dosis de refuerzo con dTpa en adolescentes y adultos como estrategia de prevención de tos ferina en México.

Pertussis continues to be responsible for a significant disease burden worldwide. Although immunization practices have reduced the occurrence of the disease among children, waning vaccine- and infection-induced immunity still allows the disease to affect adolescents and adults who, in turn, can transmit the disease to non-immunized or partially immunized infants. This document is the result of a meeting in Mexico City of international experts who analyzed recent medical information in order to establish the current status of the epidemiology, diagnosis and surveillance of pertussis and, especially, the value of the dTpa booster dose in adolescents and adults as a pertussis prevention strategy in Mexico.