The study examined the benefits and risks of respiratory syncytial virus (RSV) vaccination in pregnant women in South Africa, based on observations of increased preterm births in clinical trials of the Abrysvo vaccine. The benefit model estimated that vaccination would reduce RSV-related infant mortality by 25 to 100 per million live births born to vaccinated mothers. If vaccination did indeed cause premature births, the risk model suggested a 44-fold increase in neonatal mortality, meaning that the benefits would only minimally outweigh the risks (1.4 to 9 percent). The results were very sensitive to which week of pregnancy the vaccination would be given – with vaccination from 27 weeks of pregnancy, the benefits outweighed the risks in 97 percent of the simulations. The study was limited in that it only considered mortality associated with RSV and preterm birth, without considering other health outcomes. The authors conclude that the RSVpreF vaccine could be safe and effective if used from the third trimester of pregnancy.