Respiratory syncytial virus (RSV) is the most important cause of viral lower respiratory tract illness (LRI) in infants and children worldwide and causes significant LRI in the elderly and in immunocompromised patients. The goal of RSV vaccination is to prevent serious RSV-associated LRI. There are several obstacles to the development of successful
RSV vaccines, including the need to immunize very young infants, who may respond inadequately to vaccination; the existence of two antigenically distinct RSV groups, A and B; and the history of disease enhancement following administration of a
formalin-
inactivated vaccine. It is likely that more than one type of
vaccine will be needed to prevent RSV LRI in the various populations at risk. Although vector delivery systems, synthetic
peptide, and immune-stimulating complex
vaccines have been evaluated in animal models, only the purified F
protein (PFP)
subunit vaccines and live
attenuated vaccines have been evaluated in recent clinical trials. PFP-2 appears to be a promising
vaccine for the elderly and for RSV-seropositive children with underlying
pulmonary disease, whereas live cold-passaged (cp), temperature-sensitive (ts)
RSV vaccines (denoted cpts
vaccines) would most probably be useful in young infants. The availability of
cDNA technology should allow further refinement of existing live attenuated cpts candidate
vaccines to produce engineered
vaccines that are satisfactorily attenuated, immunogenic, and phenotypically stable.