Serosurveillance for vaccine-preventable diseases: A look inside the pertussis experience / Serovigilancia de enfermedades prevenibles por vacunación: una mirada desde la experiencia con la tosferina

Abstract Introduction: Serological surveillance (serosurveillance) provides the most direct measure of herd immunity of vaccine-preventable diseases. Little is known about the opportunities and challenges of serosurveillance experiences, particularly pertussis. Objective: To describe the process of serosurveillance for vaccine-preventable diseases with an emphasis on the experience of pertussis in the metropolitan area of Antioquia (Valle de Aburrá) in 2015 and 2016 and analyze the contributions and challenges for its sustainability. Materials and methods: We described the planning and conduction of serosurveillance of pertussis antibodies of mothers and in the umbilical cord at the time of delivery in eight hospitals based on random sampling and their capacity to advance the serosurveillance periodically. We compared the contributions and the challenges of this experience with other probabilistic and non-probabilistic programs. Results: We achieved the participation of hospitals and mothers respecting the delivery care process. We established a serum bank following ethical and technical guidelines. This program based on the random selection of hospitals and mothers has enabled the estimation of antibodies prevalence in mothers and in the umbilical cord, which has been possible given the high coverage of hospital care during childbirth at a lower cost and fewer risks than a population-based survey in conflictive areas. The main challenges for the sustainability of this program are the creation of stable jobs and access to funding and legal and methodological long-term frameworks. Conclusions: Hospital serosurveillance as described is an option to monitor the impact of vaccination on the population. Our experience could be reproduced in other regions under similar conditions if the above-mentioned challenges are solved.

Resumen Introducción. La vigilancia serológica es la forma más directa de medir la inmunidad de rebaño frente a las enfermedades prevenibles por vacunación. Poco se sabe acerca de las oportunidades y los desafíos de las experiencias de serovigilancia, en general y, específicamente, la de la tosferina. Objetivo. Describir el proceso de serovigilancia de enfermedades prevenibles por vacunación con énfasis en la experiencia en el caso de la tosferina en el área metropolitana de Antioquia (Valle de Aburrá) en el 2015 y el 2016 y analizar lo que dicha experiencia ha aportado y los desafíos que persisten para su sostenibilidad. Materiales y métodos. Se describió el proceso de planeación y el desarrollo de la serovigilancia de tosferina en el momento del parto en ocho hospitales seleccionados al azar, así como la capacidad para adelantar el programa de manera periódica. Se compararon los aportes y los desafíos en el curso de esta experiencia con los de otros programas poblacionales probabilistas e institucionales no probabilistas. Resultados. Se logró la participación de los hospitales y de las madres con pleno respeto del proceso de atención del parto, y se conformó un banco de sueros siguiendo lineamientos éticos y técnicos. El programa permitió estimar la prevalencia de anticuerpos en la madre y en el cordón umbilical, lo que se facilitó por la alta cobertura de atención hospitalaria del parto, a un menor costo y menos riesgos que los programas poblacionales en zonas conflictivas. Los principales desafíos para la sostenibilidad del programa son la estabilidad laboral del personal de salud, así como normas y una financiación de largo plazo. Conclusiones. La serovigilancia hospitalaria es una opción para monitorizar el impacto poblacional de la vacunación. Esta experiencia se podría extender a otras regiones en condiciones similares si se resuelven los retos mencionados.

Seroprevalencia contra Bordetella pertussis en embarazadas vacunadas y no vacunadas y neonatos en un hospital universitario de la provincia de Buenos Aires / Seroprevalence of Bordetella pertussis among vaccinated and unvaccinated pregnant women and newborn infants in a university hospital of Buenos Aires

Introducción. La tos convulsa es una enfermedad altamente contagiosa causada por Bordetella pertussis. Tiene una alta tasa de morbilidad y mortalidad, especialmente, en los lactantes menores de seis meses de edad. En la Argentina, la incidencia y la mortalidad se han encontrado en aumento en las últimas 3 décadas. Objetivo. Determinar anticuerpos contra Bordetella pertussis en las mujeres embarazadas en el tercer trimestre de la gestación y en el recién nacido, medidos en la sangre del cordón. Métodos. Se disenó un estudio observacional, transversal. El estudio se inició en 2011 cuando la vacunación contra pertussis en la embarazada no estaba incluida en el Calendario Nacional de Vacunación y era opcional. Los anticuerpos se midieron en las madres en el tercer trimestre del embarazo y en la sangre del cordón umbilical al nacer. Las determinaciones de anticuerpos se realizaron con el kit de ELISA humano para IgG toxina pertussis ABCAMR. Se utilizó la prueba de chi² para comparar la prevalencia. Resultados. Se incluyó a 111 madres y a sus bebés, 35 hijos de madres no vacunadas (antes de la implementación de la vacuna en embarazadas) y 76 hijos de madres vacunadas. Los bebés de madres vacunadas presentaron anticuerpos IgG positivos en el 92% (70/76), mientras que los bebés de madres no vacunadas fueron negativos para anticuerpos IgG en el 100% (35/35) con una p < 0,001. Conclusión. En la población de vacunadas del estudio, se observó que sus hijos presentaron anticuerpos IgG positivos en el 92%. Este estudio apoya la necesidad de la inmunización materna contra Bordetella pertussis para proteger al recién nacido.

Introduction. Pertussis is a highly contagious disease caused by Bordetella pertussis. It poses a high morbidity and mortality rate, especially among infants younger than 6 months old. In Argentina, pertussis incidence and mortality have increased over the past three decades. Objective. To establish Bordetella pertussis antibody titers among pregnant women in their third trimester and among newborn infants, as measured in cord blood. Methods. This was an observational, crosssectional study. The study started in 2011; at that time, pertussis vaccination was not mandatory for pregnant women as per the national immunization schedule, only optional. Maternal antibodies were measured in the last trimester of pregnancy for women and in cord blood for newborn infants. Antibody titers were determined using Abcam's anti-Bordetella pertussis toxin (PT) IgG in vitro ELISA kit. The X2 test was used to compare prevalence rates. Results. The study included 111 mother-newborn infant dyads; 35 infants from unvaccinated mothers (before the introduction of the vaccine) and 76 from vaccinated mothers. Positive IgG antibodies were found in 92% (70/76) of infants born from vaccinated mothers whereas 100% (35/35) of infants born from unvaccinated mothers had negative results for antibodies; p < 0.001. Conclusion. In the vaccinated population of this study, 92% of infants had positive IgG antibodies. This study supports the need for maternal immunization against Bordetella pertussis to provide protection to newborn infants.

Pertussis Seroprevalence in Korean Adolescents and Adults Using Anti-Pertussis Toxin Immunoglobulin G

This study was conducted to evaluate age-specific seroprevalence of pertussis in Korea and to formulate a strategy to prevent and reduce the incidence of pertussis. Residual serum samples of healthy adolescents and adults 11 yr of age or older were collected between July 2012 and December 2012, and anti-pertussis toxin (PT) IgG titers were measured using a commercial ELISA kit. We compared the mean anti-PT IgG titers and seroprevalence of pertussis of the six age groups: 11-20, 21-30, 31-40, 41-50, 51-60, and > or = 61 yr. A total of 1,192 subjects were enrolled. The mean anti-PT IgG titer and pertussis seroprevalence were 35.53 +/- 62.91 EU/mL and 41.4%, respectively. The mean anti-PT IgG titers and seroprevalence were not significantly different between the age groups. However, the seroprevalence in individuals 51 yr of age or older was significantly higher than in individuals younger than 51 yr (46.5% vs 39.1%, P = 0.017). Based on these results, a new pertussis prevention strategy is necessary for older adults.

Pertussis seroimmunity among mother-infant pairs and infant immune response to pertussis vaccination.

This study was designed to evaluate seroprevalence rates of antibodies to pertussis in mothers and their infants, and the immunogenicity of pertussis vaccine in the presence or absence of pertussis antibodies in infants. Blood samples were collected from 110 mother-infants pairs before the first dose of pertussis vaccination and from 69 infants 4-8 weeks after administration of the third dose of DTwP vaccine. Pertussis antibodies were >25 U/mL in 88(78.9%) mothers and 50(45.3%) infants with a mean titer of 67(SD 48.1) and 33.5 (34.7) U/mL, respectively. After administration of three doses of DTwP vaccine, 53(76.8%) infants were seroconverted (MCA titer 87.4 (51.3)U/mL. Immunologic response to vaccination was similar between the two groups of infants; 30/37 (81.1%) of seronegative infants and 23/32 (71.9%) of seropositive infants at pre-vaccination, showed seroconversion after the vaccination (P = 0.36). The results of this study demonstrated that most of the studied mothers were serologically immune to pertussis, and this immunity was transferred to their infants. Pre-vaccination antibody did not affect infants immune response to vaccination.