Respiratory syncytial virus (RSV) infection in the elderly and older adults with comorbidities may lead to death or severe complications that require hospitalization. At an industry-sponsored symposium during the Advances in Medicine 2026 conference, Dr Ken Ka-Pang Chan of the Department of Medicine and Therapeutics, Chinese University of Hong Kong, discussed the role of vaccination and clinical impact of the recombinant adjuvanted RSVPreF3 vaccine, especially in adults with underlying high-risk conditions such as cardiovascular (CV) and metabolic disease, asthma, and chronic obstructive pulmonary disease (COPD).
RSV infection in older adults: Rising incidence, burden, susceptibility factors
“In Hong Kong, data from the Hospital Authority and Centre of Health Protection [CHP] indicate a substantial rise in the incidence of RSV infection in older adults [aged ≥64 years] over the years, shifting from a disease affecting predominantly young children [aged <2 years] a decade ago, to one with comparable incidence in the older population,” said Chan. “Notably, among those with comorbidities, more than one-third of RSV-infected patients had chronic lung disease, asthma and COPD.” [Open Forum Infect Dis 2026;13:ofaf695.889]
Disease burden in the older population is reflected in higher RSV-associated hospitalization rate of 60–160/100,000 population for those aged ≥75 years (vs 45–97/100,000 for all ages combined), and higher annual cumulative mortality rate of 1.2–1.8/100,000 for those aged ≥65 years (vs only one fatal case recorded for children aged <5 years) between 2016 and 2024 (excluding COVID-19 pandemic period from 2020–2022), according to CHP’s surveillance data. (Table 1) [Communicable Diseases Watch 2025;21:1]
“In addition to old age, other risk factors contributing to RSV susceptibility and infection-associated complications and mortality include immunocompromised state, multimorbidity, and institutionalization [eg, in elderly homes],” noted Chan. (Table 1) [www.cdc.gov/rsv/adults/index.html; Clin Infect Dis 2022;74:1004-1011]
“RSV infection could trigger acute CV events, exacerbation of asthma and COPD, and worsening of pre-existing comorbidities,” he added. (Table 1) [Am Coll Cardiol 2018;71:1574-1583; Physiol Rev 2018;98:1417-1464; JAMA Netw Open 2026;9:e2556767; Curr Allergy Asthma Rep 2025;25:14; JAMA Intern Med 2024;184:602-611; Hum Vaccin Immunother 2025;21:2479334]
An Italian retrospective cohort study of adults aged ≥50 years with ≥1 hospitalization discharge diagnosis for RSV in 2010–2021 (n=243) and comorbidities (COPD, 37.9 percent; diabetes, 21.8 percent; heart failure [HF], 15.2 percent) found that during the index hospitalization or the 12 months that followed, 5.8 percent had an intensive care unit admission, 8.2 percent had a stroke, and 3.3 percent had an acute MI. During the 12-month follow-up period, approximately half experienced worsening of comorbidities (COPD, diabetes, HF, and renal disease), with notable rates of any-cause re-hospitalization (44.4 percent) and mortality (29.6 percent). [Hum Vaccin Immunother 2025;21:2479334]
Adjuvanted RSVPreF3 vaccine: Persistent efficacy over 3 RSV seasons
The recombinant adjuvanted RSVPreF3 vaccine protects against both RSV-A and -B subtypes and is indicated for active immunization for prevention of lower respiratory tract disease (LRTD) caused by RSV in adults aged ≥60 years, as well as those aged 50–59 years who are at increased risk of RSV disease. The vaccine’s adjuvant system boosts cellular immune response and restores RSVPreF3 CD4+ T-cell level in older adults. [Arexvy Hong Kong Full Prescribing Information (HK092024)]
The phase III AReSVi-006 trial demonstrated that a single dose of the RSVpreF3 vaccine provides lasting protection against RSV-related LRTD over three RSV seasons (30.6 months; the longest period demonstrated by any RSV vaccine to date). Vaccine efficacy rates against severe RSV-related LRTD in older adults with ≥1 pre-existing comorbidity were 94.6 percent during season 1 (first year; 6.7 months), 74.5 percent through season 2 (17.8 months), and 71.1 percent in season 3 (30.6 months). (Table 1) [Lancet Respir Med 2025;13:517-529; N Engl J Med 2023;388:595-608; Clin Infect Dis 2024;78:1732-1744; CHEST 2024, poster 3391]
AReSVi-006 was conducted across 17 countries spanning the Northern and Southern hemispheres, and included 24,966 participants aged ≥60 years, of whom 40 percent had coexisting chronic respiratory/pulmonary disease (including COPD and asthma), chronic HF, type 1 or 2 diabetes, or advanced liver or renal disease. [N Engl J Med 2023;388:595-608]
RSVPreF3 vaccine’s safety profile
In the primary phase III trial for the adjuvanted RSVPreF3 vaccine, the formulation was well tolerated with no cases of Guillain-Barré syndrome (GBS) or acute disseminated encephalomyelitis (ADEM) reported over the 31.7 months of safety follow-up. (Table 1) [CHEST 2024, poster 3391; Lancet Respir Med 2025;13:517-529] However, because pre-licensure trials lack the sample size to reliably detect ultra-rare adverse events, post-marketing active surveillance was instituted.
“Side effects, in particular neuroimmunological diseases such as GBS, are a major concern contributing to vaccine hesitancy,” said Chan. “Although real-world data show an attributable risk of approximately 5.2 excess GBS cases per 1 million doses of RSVpreF3 vaccine administered, prompting an official warning from the US FDA, the absolute risk remains extremely small.” [www.fda.gov/safety/medical-product-safety-information/fda-requires-guillain-barre-syndrome-gbs-warning-prescribing-information-rsv-vaccines-abrysvo-and; JAMA Netw Open 2025;8:e258322]
Reassuringly, apart from GBS, a real-world US case study based on Medicare surveillance among 3.8 million beneficiaries aged ≥65 years from May 2023 to July 2024 found no statistically significant elevation in risk across 11 other prespecified health outcomes (including acute MI, atrial fibrillation, deep vein thrombosis, and encephalomyelitis excluding ADEM) following RSV vaccination. [Vaccine 2026;79:128459]
Protection against RSV-related MACE, severe asthma, COPD exacerbations
The RSVPreF3 vaccine also confers protection against clinically relevant RSV-related outcomes, as demonstrated in a US retrospective cohort study using administrative claims from Optum Research Database, which evaluated the vaccine’s effectiveness among US adults aged ≥60 years at increased risk of severe RSV disease during the 2023–2024 RSV season 1. (Table 2) [Singer, et al, 9th ReSViNET Conference 2026]
International recommendations
Favourable benefit-risk profile and cost-effectiveness of RSV vaccination in the elderly and those with co-morbidities led to recommendations for RSV vaccination in international practice guidelines. (Table 1) [MMWR Morb Mortal Wkly Rep 2024;73:696-702; www.cdc.gov/acip/downloads/slides-2025-04-15-16/06-Melgar-Surie-adult-rsv-508.pdf; goldcopd.org/wp-content/uploads/2026/01/GOLD-Pocket-Guide-2026-v1.1-20Nov2025_WMV2.pdf; www.ginasthma.org; Diabetes Care 2024;47:S52-S76]
