Respiratory syncytial virus (RSV) is the leading cause of viral lower respiratory tract illness in infants and children worldwide. The RSV disease spectrum includes rhinitis, otitis media, pneumonia, and bronchiolitis. Globally, there are approximately 64 million cases of RSV each year. In the U.S., nearly all children have been infected with RSV by two years of age. RSV is also recognized as an important cause of morbidity in the elderly.
Development of vaccines to prevent RSV infection has been complicated because:
- Host immune responses play a role in the pathogenesis of the disease.
- Naturally acquired immunity to RSV is neither complete nor durable.
- Infections recur frequently.
- Two antigenically divergent groups of RSV exist (RSV A and RSV B).
Both subunit vaccines and live attenuated vaccine candidates have been developed for RSV and have been evaluated in clinical trials. Because of concerns about disease potentiation, live attenuated vaccines are the most promising vaccine candidates for infants and young children. Vaccine candidates are evaluated sequentially in adults, older children, younger children, and infants, provided that they are shown to be sufficiently attenuated for progression from one evaluation group to the next.
National Center for Infectious Diseases, Respiratory and Enteric Viruses Branch
Initiative for Vaccine Research