[Prevention of respiratory syncytial virus infection in infants. What has been done and where are we today?] / Prevención de la infección por virus respiratorio sincicial en lactantes. ¿Qué se ha hecho y en qué estamos hoy?

Respiratory syncytial virus (RSV) infection is a frequent cause of morbidity and mortality in children. Recently, great advances have been made in the development of new monoclonal antibodies and vaccines thanks to the recognition of the structural conformation of virus proteins. The objective of this study was to review the advances related to the prevention of RSV infection in the first 6 months of life. Advances in structural biology have shown that the RSV fusion protein (F-Protein) in its prefusion state (Pre-F) is an excellent antigen for developing monoclonal antibodies and vaccines to prevent respiratory syncytial virus (RSV) infections. A new single-dose monoclonal antibody, Nirsevimab, has greater neutralizing power than currently available Palivizumab, and prolonged protection for 5 to 6 months. Nirsevimab has demonstrated an efficacy of 76.8% (95% CI, 49.4 to 89.4) in preventing lower respiratory infection 150 days after vaccination, decreasing the risk of ICU admission by 90.1% (95% CI: 16.4-98.8). Clesrovimab is another single-dose monoclonal antibody that has also shown promising results in phase 1b-2a trials. More recently, a bivalent vaccine against RSV A and B (Bivalent Prefusion F) has also been developed by replicating the F-protein stabilized in its Pre-F state as an antigen, using genetic engineering. This antigen, when administered to pregnant women between 24-36 weeks of gestation, induces high levels of antibodies in the mother with high transplacental transfer to the fetus. This vaccine has demonstrated an efficacy of 81.8% (95% CI: 40.6-96.3) at 90 days and 69.4% (95% CI: 44.3-84.1) at 180 days to prevent severe RSV disease (primary endpoint) without safety events detected so far. Nirsevimab and the Pre-F vaccine for pregnant women confer effective protection through passive immunity against RSV that lasts for the first 5 to 6 months of life and have already been approved for use in Europe by the EMA and in Canada and the United States by the FDA.

Betametasona fosfato para la prevención de Síndrome de Dificultad Respiratoria (SDR) del recién nacido de pretérmino / Betamethasone phosphate for the prevention of Respiratory Distress Syndrome (RDS) in the preterm newborn

RESUMEN Introducción: El estándar para inducción de madurez pulmonar en fetos con riesgo de nacer prematuramente es la administración de 12 mg de betametasona acetato/fosfato por dos veces espaciada cada 24 horas. El uso establecido en algunos hospitales públicos en Chile es con dos dosis de 12 mg betametasona fosfato aunque no existen estudios publicados sólo con betametasona fosfato sobre la incidencia de Síndrome de Distress Respiratorio (SDR). Objetivo: Evaluar efecto de betametasona en su forma fosfato como tratamiento antenatal para inducción de madurez fetal pulmonar en la incidencia SDR debido a membrana hialina en prematuros menores de 34 semanas de edad gestacional. Comparar el efecto de betametasona fosfato con el efecto publicado de betametasona acetato/fosfato. Material y método: Análisis de incidencia de SDR en prematuros nacidos en Hospital Padre Hurtado entre 24+0 y 34+0 semanas que recibieron betametasona fosfato para madurez pulmonar y aquellos que no la recibieron. Resultados: De 1.265 neonatos estudiados, 722 completaron dos dosis (57,5%); 436 sólo una dosis (34,5%) y 107 (8,5%) no recibieron corticoides antenatales. La incidencia de SDR debido a membrana hialina en el grupo con dos dosis fue 8,7%, una dosis 25,3% y 32,7% en los no tratados (p<0,001). Para SDR severo las incidencias fueron 6,7%, 12,6% y 16,8% respectivamente (p<0,001). Conclusiones: Inducción de madurez fetal pulmonar con betametasona fosfato en dos dosis de 12 mg IM separadas por 24 horas otorga una reducción significativa de incidencia de SDR semejante a la publicada con betametasona acetato/fosfato en iguales dosis.

ABSTRACT The standard for induction of lung maturity in fetuses at risk of being born prematurely is the administration of 12 mg of betamethasone acetate/phosphate two doses separated by 24 hours. The established use in some public hospitals in Chile is with two doses of 12 mg betamethasone phosphate although there are no studies published with betamethasone phosphate alone on the incidence of respiratory distress syndrome (RDS). Objective: To evaluate the effect of betamethasone in its phosphate form as antenatal treatment for the induction of fetal lung maturity in the incidence of RDS due to hyaline membrane in preterm infants less than 34 weeks of gestational age. To compare the effect of betamethasone phosphate with the published effect of betamethasone acetate/phosphate. Material and method: Analysis of the incidence of RDS in preterm infants born at Hospital Padre Hurtado between 24 + 0 and 34 + 0 weeks who received betamethasone phosphate for lung maturity and those who did not receive it. Results: Of 1,265 infants studied, 722 completed two doses (57.5%); 436 only one dose (34.5%) and 107 (8.5%) did not receive antenatal corticosteroids. The incidence of RDS due to hyaline membrane in the group with two doses was 8.7%, one dose 25.3% and 32.7% in the untreated ones (p <0.001). For severe RDS, incidences were 6.7%, 12.6% and 16.8% respectively (p <0.001). Conclusions: Induction of fetal lung maturity with betamethasone phosphate in two doses of 12 mg IM separated by 24 hours gives a significant reduction in the incidence of RDS similar to that published with betamethasone acetate/phosphate in equal doses.