ABSTRACT
Respiratory syncytial virus (RSV) and parainfluenza virus types 1, 2, and 3 (PIV1, PIV2, and PIV3) are responsible for more than 40% of viral respiratory tract disease leading to hospitalization of infants and children. For this reason, there is a need to develop vaccines effective against these viruses. Because RSV and PIV3 cause severe lower respiratory tract disease in early infancy, vaccines for these viruses must be effective in immunologically immature recipients who have circulating maternal antibodies. To date, several strategies for immunization against disease caused by these viruses have been explored including peptide vaccines, inactivated or subunit vaccines, vectored vaccines (e.g., vaccinia-RSV or adenovirus-RSV recombinants), and live-attenuated virus vaccines. The most promising approaches are summarized in Table 1. The status of these approaches is reviewed. In addition, the immunologic basis for the disease potentiation seen in vaccinees immunized with formalininactivated RSV during subsequent RSV infection is reviewed. The efficacy of immunization in the presence of maternal antibodies is discussed.
