**5. Conclusions**

RSV is one of the most common causes of lower respiratory disease in infants, young children, and the elderly. Treatment is currently limited to supportive care, such as supplemental oxygen, bronchodilators, or corticosteroids. Palivizumab prophylaxis is currently restricted to high-risk infants. There is currently no vaccine to prevent RSV infection. There are many challenges associated with developing an RSV vaccine candidate. When developing a live attenuated vaccine, an equilibrium must be struck between adequate immunogenicity and attenuation of the virus. Non-replicating vaccines, like in some vector-delivery systems and protein-based vaccines, can enhance RSV infection in RSV-naïve infants. Therefore, it may be necessary to develop separate vaccines for each at-risk population: neonates and young children, pregnant women, and the elderly. One highly promising strategy appears to be maternal immunization with a nonreplicating vaccine, as this may provide protection during the first few months of life in the neonate.
