Statistical analysis
Mean and standard deviation (SD) were calculated to describe clinical continuous variables. Concerning antibody titers against RSV N, both mean (SD) and median (interquartile range, IQR) were calculated. Comparisons between mean antibody titers were tested using a 2-sided parametric Student t-test or an ANOVA for more than 2 groups. The birth weight and the gestational age were treated as categorical variables. A generalized linear model (GLM) was used to test the occurrence of a VS-LRTI in function of sex, mode of delivery, parity of the mother, type of pregnancy, date of birth in relation to the peak of the epidemic, and titer antibodies against RSV N (quantitative variable). Preterm infants as well as patients who contracted a VS-LRTI but for whom the result for RT-PCR RSV detection was negative were excluded from the GLM. Statistical analyses were performed using R software version 4.0.3.