RSV is one of the most important agents of lower respiratory infections in childhood. In this study, anti-RSV antibody levels in mother-infant pairs and factors related to antibody transfer ratio were investigated. One hundred and twenty-seven women that had term babies and their babies and 84 mother-infant pairs of them who continued the study after 6 months were enrolled. Anti-RSV IgG antibodies of the mothers and infants were positive in 46.5% and 61.5%, respectively. At the sixth month, anti-RSV antibodies were negative in all infants. Median of the anti-RSV antibody levels of the mothers and infants at birth were 12.08 IU/ml (1.21-119.27) and 13.78 IU/ml (3.99-108.6), respectively. There was a significant correlation between anti-RSV antibody levels of mothers and infants at birth (p: 0.0001, r: 0.667) and anti-RSV antibody levels of infants at birth and at 6th month (p: 0.0001, r: 0.343). Median ratio of infant and mother antibody levels was 1.22 (0.14-6.05). Median ratio that was detected in appropriate for gestational age infants was significantly higher than in small for gestational age or large for gestational age infants. In this study, the significant positive correlation between maternal antibody levels and infants' antibody levels at birth suggests that maternal vaccination strategies may be logical. We showed that antibody transfer rate was highest in appropriate for gestational age infants. It should be kept in mind that maternal vaccination strategies may be less effective in small for gestational age and large for gestational age infants.
Keywords: Maternal antibodies; Passive immunization; Respiratory syncytial virus; Transplacental antibody transfer.