Schwarz TF, Johnson C, Grigat C, et al. - Respiratory tract infections caused by respiratory syncytial virus (RSV) may lead to hospitalization especially in early infancy. Researchers herein examined whether transplacental transfer of RSV antibodies could confer protection to infants in their first months of life. In this first-in-human, placebo-controlled study, a single dose of unadjuvanted vaccine containing 30/60/120 µg of RSV fusion (F) protein stabilized in the prefusion conformation (RSVPreF3), or placebo was administered to 502 healthy non-pregnant women. Outcomes revealed the RSVPreF3 vaccine to be well tolerated and immunogenic. The higher dose levels were noted to be significantly more immunogenic than the lowest one when comparisons at D8 and D31 were performed. They selected 60 and 120 µg dose levels for further evaluation in pregnant women.