Review Current State and Challenges in Developing Respiratory Syncytial Virus Vaccines Carlotta Biagi 1, Arianna Dondi 1,* , Sara Scarpini 1 , Alessandro Rocca 1, Silvia Vandini 2, Giulia Poletti 1 and Marcello Lanari 1 1 Pediatric Emergency Unit, Department of Medical and Surgical Sciences (DIMEC), Sant’Orsola University Hospital, 40138 Bologna, Italy;
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[email protected]; Tel.: +39-051-2144635; Fax: +39-051-2144440 Received: 14 October 2020; Accepted: 10 November 2020; Published: 11 November 2020 Abstract: Respiratory syncytial virus (RSV) is the main cause of acute respiratory tract infections in infants and it also induces significant disease in the elderly. The clinical course may be severe, especially in high-risk populations (infants and elderly), with a large number of deaths in developing countries and of intensive care hospitalizations worldwide. To date, prevention strategies against RSV infection is based on hygienic measures and passive immunization with humanized monoclonal antibodies, limited to selected high-risk children due to their high costs. The development of a safe and effective vaccine is a global health need and an important objective of research in this field. A growing number of RSV vaccine candidates in different formats (particle-based vaccines, vector-based vaccines, subunit vaccines and live-attenuated vaccines) are being developed and are now at different stages, many of them already being in the clinical stage.