Humoral immune response to measles and varicella vaccination in former very low birth weight preterm infants

ABSTRACT Introduction: Immune response to vaccination in infants born prematurely may be lower than in infants born at full-term. Some clinical factors might be associated with humoral immune response. Objectives: The objectives of this study were to compare the immune response to measles and varicella vaccination in infants born prematurely with those born at full-term and to analyze factors associated with measles and varicella antibody levels. Methods: Prospective study including two groups of infants aged 12 months. One group of infants born prematurely with birth-weight <1500 g and who were in follow-up at the outpatient clinic for preterm infants at the institution and other group of infants born at full-term. Infants with malformations, primary immunodeficiency diseases, born to HIV-positive mothers or who had received plasma or immunoglobulin transfusions five months before or three weeks after vaccination were excluded. Plasma antibodies were measured by ELISA and factors associated with antibody levels were assessed by linear regression. Results: Sixty-five premature and 56 full-term infants were included. The percentage of immune individuals after vaccination against measles (100% vs. 100%) and varicella (92.5% vs. 93.2%) were similar in both groups, as well as the antibody levels against measles (2.393 vs. 2.412 UI/mL; p = 0.970) and varicella (0.551 vs. 0.399 UI/mL; p = 0.114). Use of antenatal corticosteroids decreased measles antibody levels whereas breastfeeding for more than six months increased varicella antibody levels. Conclusions: Humoral responses to measles and varicella were similar between infants born prematurely and full-term infants. Measles antibody levels were negatively associated with antenatal corticosteroid use; varicella antibodies were positively associated with prolonged breastfeeding.

Efectividad de la vacuna antivaricela como profilaxis post exposición en niños chilenos / Effectiveness of varicella vaccine as post exposure prophylaxis in Chilean children

Introduction: Efficacy and effectiveness of varicella vaccine (VV) as post exposure prophylaxis (PEP) strategy have shown discordant results for disease risk reduction, and more consistent results in their ability to attenuate the disease. Aim: To assess the effectiveness of VV as PEP among household contacts. Material and Methods: We followed up 33 children after household exposure to a varicella case, of which 15 received VV as PEP and 18 did not received VV. The presence and severity of the disease were clinically determined. Results: Secondary attack rate was 53% among vaccinated and 89% among non-vaccinated children. Overall effectiveness of VV as PEP was 40% (CI95% 1%-64%). The effectiveness for preventing moderate or severe disease was 63% (CI95% 8%-85%) in the entire group and 77% (CI95% 14%-94%) among children vaccinated during the first 3 days post exposure. Vaccine tolerance was acceptable, with a low number of adverse reactions, all of them mild. Conclusion: The results suggest that VV as PEP is effective among household contacts, especially for reducing the severity of the disease.

Introducción: Los estudios de eficacia y efectividad de la vacuna antivaricela (V AV) como profilaxis post exposición (PPE) han mostrado resultados disímiles en cuanto a la reducción del riesgo de enfermar, y algo más consistentes en su capacidad de atenuar la enfermedad. Objetivo: Evaluar la efectividad de la VAV como PPE utilizada en contactos domiciliarios. Material y Métodos: Se realizó el seguimiento post exposición de 33 contactos domiciliarios de casos de varicela, de los cuales 15 recibieron VAV como PPE y 18 no la recibieron. Se determinó clínicamente el desarrollo de enfermedad y la intensidad de la misma. Resultados: La tasa de ataque secundario fue 53% en vacunados y 89% en no-vacunados, siendo la efectividad global de la VAV como PEP 40% (IC95% 1%-64%). La efectividad para prevenir enfermedad moderada o intensa fue 63% (IC95% 8-85%) en el grupo completo y 77% (IC95% 14-94%) en los niños vacunados durante los primeros tres días post exposición. La tolerancia a la vacuna fue aceptable, con un bajo número de reacciones adversas, todas leves. Conclusión: Los resultados sugieren que la VAV es efectiva como PPE en contactos domiciliarios, especialmente para reducir la intensidad de la enfermedad.

Estudio de un brote de varicela en un pueblo del Uruguay / Varicella outbreak in a village in Uruguay

A varicella outbreak occurred in a Uruguayan village that introduced the varicella vaccine in 1999 with currently high vaccination rates. Aim: To investigate the cause of the outbreak, vaccine effectiveness, and to describe the measures adopted. Material and Methods: Cases that occurred in the kindergarten and schools in the village were investigated. Vaccination cards were examined, history of chickenpox and clinical characteristic of the current episode were obtained and the outcome of the measures was evaluated. An estimate was made of the vaccine's effectiveness. Results: 37 cases of varicella were reported, 14 occurring in previously vaccinated children, in a one total population of 313 children. The global effectiveness of the vaccine was 80 percent, and 100 percent for severe cases. A shift of cases towards older ages was demonstrated; vaccinated children had a trend of less fever and lower number of lesions. Immunization of healthy unvaccinated children, mainly adolescents stopped the outbreak. Comments: The vaccine proved to be highly effectiveness. In an outbreak situation, immunization policies should consider "catch up" vaccination in non-immunized adolescents without a previous history of varicella.

Un brote de varicela acaeció en un pueblo uruguayo que había introducido la vacunación anti-varicela en 1999 y tenía altas coberturas de vacunación. Objetivo: Investigar las causas del brote, la efectividad de la vacunación y evaluar las medidas adoptadas. Material y Métodos: Se investigó los casos ocurridos enjardines de infantes y colegios. Se revisó el carné de vacunación de cada niño además de averiguar por historia previa de varicela, las características clínicas de los casos y el resultado de las medidas adoptadas. Se hizo una estimación de la efectividad de la vacuna. Resultados: Se presentaron 37 casos de varicela, 14 de los cuales habían recibido la vacuna, en una población total de 313 niños. La efectividad global de la vacuna fue de 80 por ciento, y de 100 por ciento para los casos graves. Se constató un desplazamiento de la enfermedad hacia edades mayores; además, los casos en vacunados tuvieron una tendencia a presentar menos fiebre y un número menor de lesiones. La vacunación de aquellos que no habían tenido la varicela y no estaban vacunados antes, detuvo el brote epidémico. Comentarios: Se demostró la efectividad de la vacuna. La política de vacunación debiera evaluar si es necesario proceder a la vacunación "de rescate" en adolescentes no vacunados y que no exhiben el antecedente de haber padecido la varicela.

Differentiation of wild-type varicella-zoster strains from India and the Oka vaccine strain using a VZV open reading frame - 62 based PCR-RFLP technique

Since the introduction of varicella vaccination in India, surveillance of circulating VZV strains has gained significance. Differentiating wild-type VZV strains from the Oka vaccine strain can be achieved only by molecular genotyping methods. The development of PCR methods for VZV strain differentiation has been hampered by the fact that the VZV genome is highly conserved. We used VZV ORF 62 PCR-RFLP analysis to identify and differentiate wild-type VZV strains in India from the Oka vaccine strain. Digestion of VZV ORF 62 amplicons with SmaI, enabled accurate strain differentiation; the Oka strain was positive for three SmaI sites, compared to two SmaI sites in the wild-type VZV strains that we tested.

Imunidade para varicela entre habitantes de Belém, PA, Brasil / Chickenpox immunity among Belém (PA) Brazil inhabitants

Objetivo: Conhecer o estado imunitário para a varicela em indivíduos de diversas faixas etárias da Cidade de Belém, no Estado do Pará, norte do Brasil, para a tomada de decisäo quanto à indicaçäo de vacinaçäo. Método: Os soros de 525 indivíduos residentes na Cidade de Belém, separados aleatoriamente da soroteca de dois laboratórios privados de análise clínicas e do Instituto Evandro Chagas, foram testados pelo método imunoenzimático (ELISA). Resultados: Dos 525 soros testados 22,2 por cento, 5l,7 por cento , 72,9 por cento e 92,5 por cento foram positivos nas faixas etárias de 0-4, 5-14, 15-24 e > e igual 25 anos, respectivamente. Conclusöes: Näo obstante a grande concentraçäo da varicela nos primeiros dez anos de vida, cerca da metade dos adolescentes e adultos jovens persistem sem imunidade. Este achado sugere que há indicaçäo da vacinaçäo contra a varicela para as crianças, mas também, e principalmente, para os adolescentese adultos jovens, sem história consistente de doença correlata, uma vez que nesses grupos de faixas etárias maiores, a infecçäo pode evoluir com doença mais grave, com risco de complicaçöes e óbito.