The RSV is the biggest cause of viral lower respiratory tract illness (LRI) in infants and children, and it causes significant LRI in elderly and in immunocompromised patients, according to the National Institutes of Health (NIH). The need to immunize very young infants, who may respond inadequately to vaccination; the existence of two antigenically distinct RSV groups, and the history of disease enhancement following administration of a formalin-inactivated vaccine are three obstacles for developing an effective vaccine. There is no vaccine yet, but there is a medicine (called palivizumab), which is a series of monthly shots, according to the CDC.