Randomized clinical trial of the safety and immunogenicity of the Tdap vaccine in pregnant Mexican women.

Immunization with the tetanus, diphtheria, and pertussis (Tdap) vaccine raises controversies on immunogenicity and possible antibody interference. We performed an experimental, double-blind, parallel group controlled clinical trial to evaluate the safety and immunogenicity of the Tdap vaccine in 204 pregnant women and their children and to determine its interference in antibody production. Pregnant women 18 to 38 y of age with 12 to 24 weeks gestation, a low obstetric risk, and without serious disease were randomly selected. The experimental group received 0.5 mL IM of Tdap and the control group normal saline. Six blood samples were drawn before and after solution application, and from the umbilical cord of the infants and at 2, 4, and 6 months of age. Pertactin and Pertussis toxin antibodies and possible interference of maternal antibodies with the vaccine were determined. In the experimental group, antibodies against Bordetella pertussis pertactin (anti-PRN) (112 E/mL 95% CI 89.9-139.9) and antibodies against pertussis toxin (anti-PT) (24.0 E/mL, 95% CI 18.3-31.4) were elevated in the mother before vaccination. These were higher in the umbilical cord and descended in the infant at 2 months (71.4 (95% CI 56.8-89.7 and 10.9; 95% CI 8.7-13.7, respectively). Anti-PT showed a delay in production. Tdap safety was confirmed with only mild local pain at 24 and 48 hours. Anti-PRN and anti-PT antibodies in the infant descend at 2 months of age. There is a delay in anti-PT in children of immunized mothers. Further studies are needed to elucidate its clinical significance.

Evaluation of a new syringe presentation of reduced-antigen content diphtheria, tetanus, and acellular pertussis vaccine in healthy adolescents--A single blind randomized trial.

Reduced-antigen-content diphtheria-tetanus-acellular pertussis (dTpa) vaccine, Boostrix™, is indicated for booster vaccination of children, adolescents and adults. The original prefilled disposable dTpa syringe presentation was recently replaced by another prefilled-syringe presentation with latex-free tip-caps and plunger-stoppers. 671 healthy adolescents aged 10-15 years who had previously received 5 or 6 previous DT(P)/dT(pa) vaccine doses, were randomized (1:1) to receive dTpa booster, injected using the new (dTpa-new) or previous syringe (dTpa-previous) presentations. Immunogenicity was assessed before and 1-month post-booster vaccination; safety/reactogenicity were assessed during 31-days post-vaccination. Non-inferiority of dTpa-new versus dTpa-previous was demonstrated for all antigens (ULs 95% CIs for GMC ratios ranged between 1.03-1.13). 1-month post-booster, immune responses were in similar ranges for all antigens with both syringe presentations. dTpa delivered using either syringe presentation was well-tolerated. These clinical results complement the technical data and support the use of the new syringe presentation to deliver the dTpa vaccine.

A correlation of measles specific antibodies and the number of plasmacytoid dendritic cells is observed after measles vaccination in 9 month old infants.

Measles virus (MeV) represents one of the main causes of death among young children, particularly in developing countries. Upon infection, MeV controls both interferon induction (IFN) and the interferon signaling pathway which results in a severe host immunosuppression that can persists for up to 6 mo after infection. Despite the global biology of MeV infection is well studied, the role of the plasmacytoid dendritic cells (pDCs) during the host innate immune response after measles vaccination remains largely uncharacterized. Here we investigated the role of pDCs, the major producers of interferon in response to viral infections, in the development of adaptive immune response against MeV vaccine. We report that there is a strong correlation between pDCs population and the humoral immune response to Edmonston Zagreb (EZ) measles vaccination in 9-month-old mexican infants. Five infants were further evaluated after vaccination, showing a clear increase in pDCs at baseline, one week and 3 months after immunization. Three months postvaccination they showed increase in memory T-cells and pDCs populations, high induction of adaptive immunity and also observed a correlation between pDCs number and the humoral immune response. These findings suggest that the development and magnitude of the adaptive immune response following measles immunization is directly dependent on the number of pDCs of the innate immune response.

Encuesta serológica nacional del sarampión en niños: evidencias para su eliminación / Measles serologic survey in Mexican children: evidence for its elimination in Mexico

OBJETIVO: Analizar la distribución y frecuencia de anticuerpos protectores contra sarampión en una muestra representativa estatal en niños de 1-9 años, así como contribuir a la evaluación de los programas de vacunación contra este agente. MATERIAL Y MÉTODOS: Se estudió la presencia de anticuerpos contra el virus del sarampión en una muestra de la Encuesta Nacional de Salud 2000. Los sueros se recolectaron de noviembre de 1999 a junio de 2000. La muestra consta de 6 270 niños y se utilizó la técnica de reducción de placas por neutralización. RESULTADOS: La seropositividad (>120 UI/L) de los niños de 1-4 años fue menor que la de los niños de 5-9 años, 98.3 por ciento (IC95 por ciento 97.7-98.8) contra 99.4 por ciento (IC95 por ciento 99.2-99.6, p<0.001). Los niveles de seropositividad se incrementaron con el número de dosis de vacuna de sarampión o sarampión-rubeola-parotiditis y no dependen de género, residencia o nivel socioeconómico. CONCLUSIONES: Los resultados muestran que existe una cobertura adecuada en la vacunación; sin embargo, al expandir los datos se observó que existen 417 000 niños que presentaron títulos negativos de anticuerpos, por lo que son susceptibles de adquirir, transmitir el virus y contribuir a la generación de brotes de la enfermedad.

OBJECTIVE: To analyze the frequency and distribution of protective antibodies against measles in a sample of children from 1-9 years old representative of each of the 32 states in Mexico; to contribute to the evaluation of the measles vaccination programs. MATERIAL AND METHODS: Measles antibodies (plaque reduction neutralization (PRN) assay) were studied in 6 270 sera selected from the 24 232 sera from children 1-9 years of age, collected by the 2000 National Health Survey (ENSA 2000) that was conducted from November 1999 to June 2000. RESULTS: Proportion of seropositive samples (>120 IU/L) among 1-4 year-old children (98.3 percent [95 percentCI: 97.7-98.8]) was less than that of 5-9 year-old children (99.4 percent [95 percentCI: 99.2-99.6]; p<0.001). Seropositivity was associated with the number of measles and/or measles-rubella-mumps vaccine doses and was not associated with gender, place of residence or socio-economic status. CONCLUSIONS: The results show that there is adequate vaccination coverage. However, the expansion of data revealed that there are 417 000 children with negative antibody titers who are susceptible to acquiring the disease, transmitting the virus and causing outbreaks.