In this episode, we briefly review RSV (respiratory syncytial virus) infections and focus on new data supporting the use of two different RSV vaccines (Abrysvo and Arvexy) in preventing RSV infections in older adults and in pregnant women. Key Concepts RSV is a contagious respiratory virus that is usually mild and self-limiting in most patients but can cause severe disease especially in young children or older adults with certain risk factors. The FDA recently approved two vaccines for RSV (Abrysvo from Pfizer and Arexvy from GSK). The initial FDA approval was for adults 60 years of age and older; however, the FDA recently granted an additional indication for Abrysvo for pregnant women (to prevent the infant from severe RSV infection once born). When studied in older adults, both vaccines did meet efficacy criteria but the incidence of RSV infection was relatively low and thus the number needed to treat (NNT) is high. Both studies were done at times with lower RSV prevalence - the NNT would likely be more favorable during RSV outbreaks. Unlike Abrysvo, Arvexy (GSK) contains an adjuvant to improve the immune response. Although direct comparisons of efficacy and safety are not appropriate, Arvexy does appear to elicit more systemic adverse effects such as fever, myalgias, headache, and fatigue. References Respiratory Syncytial Virus Infection (RSV). Centers for Disease Control and Prevention. https://www.cdc.gov/rsv/index.html Abrysvo (respiratory syncytial virus vaccine). US Food & Drug Administration. https://www.fda.gov/vaccines-blood-biologics/abrysvo Arexvy (respiratory syncytial virus vaccine, adjuvanted). US Food & Drug Administration. https://www.fda.gov/vaccines-blood-biologics/arexvy Use of Respiratory Syncytial Virus Vaccines in Older Adults: Recommendations of the Advisory Committee on Immunization Practices — United States, 2023. Morbidity and Mortality Weekly Report (MMWR). July 21, 2023 / 72(29);793-801. https://www.cdc.gov/mmwr/volumes/72/wr/mm7229a4.htm CDC. ACIP Recommendations. Last reviewed August 4, 2023. www.cdc.gov/vaccines/acip/recommendations.html. Accessed August 23, 2023. RENOIR - Walsh EE, Pérez Marc G, Zareba AM, et al. Efficacy and Safety of a Bivalent RSV Prefusion F Vaccine in Older Adults. N Engl J Med. 2023;388(16):1465-1477. doi:10.1056/NEJMoa2213836 AReSVi-006 - Papi A, Ison MG, Langley JM, et al. Respiratory Syncytial Virus Prefusion F Protein Vaccine in Older Adults. N Engl J Med. 2023;388(7):595-608. doi:10.1056/NEJMoa2209604 MATISSE - Kampmann B, Madhi SA, Munjal I, et al. Bivalent Prefusion F Vaccine in Pregnancy to Prevent RSV Illness in Infants. N Engl J Med. 2023;388(16):1451-1464. doi:10.1056/NEJMoa2216480 RSV-NET Interactive Dashboard. Centers for Disease Control and Prevention. https://www.cdc.gov/rsv/research/rsv-net/dashboard.html ACIP Meeting Information - Meeting Materials. https://www.cdc.gov/vaccines/acip/meetings/index.html