Authors: Jorge C. G. Blanco (Sigmovir Biosystems Inc.)
Recently, many programs developing respiratory syncytial virus (RSV) vaccines have sought to vaccinate pregnant women in an effort to enhance maternal immunity, with the goal of enhancing protection in neonates . RSV is the main cause of infection and respiratory disease in infants under 6 months of age, strongly justifying a maternal vaccination strategy.
The rate of hospitalization for RSV in infants is 10–28% at 6 weeks, and peaks at 44% at 2 months [2,3]. Of all severe cases of RSV infection, 65% occur in the first 6 months of life [2–4]. Importantly, maternal antibodies (matAbs) against RSV are abundant in the first months of life and decline to low titers at approximately 4–6 months of age [5–7]. Because enhanced levels of matAbs and RSV vulnerability of neonates overlap, many studies have struggled to come to any consensus on the role of matAbs in protection from RSV infection, bronchiolitis, or pneumonia [3,4, 8–13]. In addition, it is know that breast milk contains RSV neutralizing activity as well as RSV-specific antibodies . However, the role of lactation in the neonatal immune response against RSV also remains controversial [15,16]. Thus, the role of matAbs in protection of RSV-infected infants remains unknown and most likely depends of a plethora of uncontrolled factors in the mother and the infant (e.g., season of birth, developmental stage at birth, time of the last maternal exposure and the strain of RSV, if breastfeeding, etc.).