Moriyama M, Hugentobler WJ, Iwasaki A. Seasonality of respiratory viral infections. Annu Rev Virol. 2020;7(1):83–101. https://doi.org/10.1146/annurev-virology-012420-022445.

Article  CAS  PubMed  Google Scholar 

Centers for Disease Control and Prevention. About COVID-19. https://www.cdc.gov/covid/about/. Accessed 7 Mar 2024.

Centers for Disease Control and Prevention. Groups most impacted—emergency department visits. https://www.cdc.gov/respiratory-viruses/data/most-impacted.html. Accessed 7 Mar 2024.

Centers for Disease Control and Prevention. About Influenza. https://www.cdc.gov/flu/about/index.html. Accessed 7 Mar 2024.

Centers for Disease Control and Prevention. Protect yourself and others from Flu, COVID-19, and RSV. https://stacks.cdc.gov/view/cdc/96864/cdc_96864_DS1.pdf. Accessed 9 Apr 2024, Accessed 7 Mar 2024.

World Health Organization. The top 10 causes of death. https://www.who.int/news-room/fact-sheets/detail/the-top-10-causes-of-death. Accessed 6 Mar 2024.

Centers for Disease Control and Prevention. Respiratory syncytial virus (RSV) symptoms and care. https://www.cdc.gov/rsv/symptoms/. Accessed 15 Apr 2024.

Centers for Disease Control and Prevention. Key facts about influenza (flu). https://www.cdc.gov/flu/about/keyfacts.htm. Accessed March 20, 2024.

Centers for Disease Control and Prevention. People at higher risk of flu complications. https://www.cdc.gov/flu/highrisk/index.htm. Accessed 7 Mar 2024.

Centers for Disease Control and Prevention. RSV in older adults and adults with chronic medical conditions. https://www.cdc.gov/rsv/causes/. Accessed 31 July 2024.

Prasad N, Walker TA, Waite B, et al. Respiratory syncytial virus-associated hospitalizations among adults with chronic medical conditions. Clin Infect Dis. 2021;73(1):e158–63. https://doi.org/10.1093/cid/ciaa730.

Article  PubMed  Google Scholar 

Walker TA, Waite B, Thompson MG, et al. Risk of severe influenza among adults with chronic medical conditions. J Infect Dis. 2020;221(2):183–90. https://doi.org/10.1093/infdis/jiz570.

Article  PubMed  Google Scholar 

Centers for Disease Control and Prevention. RESP-NET interactive dashboard. https://www.cdc.gov/surveillance/resp-net/dashboard.html. Accessed 14 Mar 2024.

Centers for Disease Control and Prevention. Underlying medical conditions associated with higher risk for severe COVID-19: information for healthcare professionals. https://www.cdc.gov/covid/hcp/clinical-care/underlying-conditions.html. Accessed 6 Mar 2024.

Havers FP, Whitaker M, Melgar M, et al. Characteristics and outcomes among adults aged (60 years hospitalized with laboratory-confirmed respiratory syncytial virus—RSV-NET, 12 States, July 2022–June 2023. MMWR Morb Mortal Wkly Rep. 2023;72(40):1075–82. https://doi.org/10.15585/mmwr.mm7240a1.

Article  PubMed  PubMed Central  Google Scholar 

Hong R, Walker R, Hovan G, Henry L, Pescatore R. The power of public health surveillance. Dela J Public Health. 2020;6(2):60–3. https://doi.org/10.32481/djph.2020.07.016.

Article  PubMed  PubMed Central  Google Scholar 

Centers for Disease Control and Prevention. Respiratory illnesses: respiratory viruses and pregnancy. https://www.cdc.gov/respiratory-viruses/risk-factors/pregnant-people.html. Accessed 7 Aug 2024.

World Health Organization. Ageing and health. https://www.who.int/news-room/fact-sheets/detail/ageing-and-health. Accessed 7 Mar 2024.

Franceschi C, Garagnani P, Morsiani C, et al. The continuum of aging and age-related diseases: common mechanisms but different rates. Front Med (Lausanne). 2018;5:61. https://doi.org/10.3389/fmed.2018.00061.

Article  PubMed  Google Scholar 

Watson A, Wilkinson TMA. Respiratory viral infections in the elderly. Ther Adv Respir Dis. 2021;15:1753466621995050. https://doi.org/10.1177/1753466621995050.

Article  PubMed  PubMed Central  Google Scholar 

Pawelec G, Bronikowski A, Cunnane SC, et al. The conundrum of human immune system “senescence.” Mech Ageing Dev. 2020;192: 111357. https://doi.org/10.1016/j.mad.2020.111357.

Article  CAS  PubMed  PubMed Central  Google Scholar 

Lee KA, Flores RR, Jang IH, Saathoff A, Robbins PD. Immune senescence, immunosenescence and aging. Front Aging. 2022;3: 900028. https://doi.org/10.3389/fragi.2022.900028.

Article  PubMed  PubMed Central  Google Scholar 

Aiello A, Farzaneh F, Candore G, et al. Immunosenescence and its hallmarks: how to oppose aging strategically? A review of potential options for therapeutic intervention. Front Immunol. 2019;10:2247. https://doi.org/10.3389/fimmu.2019.02247.

Article  CAS  PubMed  PubMed Central  Google Scholar 

Lord J. The effect of aging of the immune system on vaccination responses. Hum Vaccin Immunother. 2013;9(6):1364–7.

Article  CAS  PubMed  PubMed Central  Google Scholar 

Clegg A, Young J. The frailty syndrome. Clin Med (Lond). 2011;11(1):72–5. https://doi.org/10.7861/clinmedicine.11-1-72.

Article  PubMed  Google Scholar 

Luna CM, Palma I, Niederman MS, et al. The impact of age and comorbidities on the mortality of patients of different age groups admitted with community-acquired pneumonia. Ann Am Thorac Soc. 2016;13(9):1519–26. https://doi.org/10.1513/AnnalsATS.201512-848OC.

Article  PubMed  Google Scholar 

O’Hare AM, Berry K, Fan VS, et al. Age differences in the association of comorbid burden with adverse outcomes in SARS-CoV-2. BMC Geriatr. 2021;21(1):415. https://doi.org/10.1186/s12877-021-02340-5.

Article  CAS  PubMed  PubMed Central  Google Scholar 

Verity R, Okell LC, Dorigatti I, et al. Estimates of the severity of coronavirus disease 2019: a model-based analysis. Lancet Infect Dis. 2020;20(6):669–77. https://doi.org/10.1016/S1473-3099(20)30243-7.

Article  CAS  PubMed  PubMed Central  Google Scholar 

Chen T, Dai Z, Mo P, et al. Clinical characteristics and outcomes of older patients with Coronavirus disease 2019 (COVID-19) in Wuhan, China: a single-centered, retrospective study. J Gerontol A Biol Sci Med Sci. 2020;75(9):1788–95. https://doi.org/10.1093/gerona/glaa089.

Article  CAS  PubMed  Google Scholar 

Blagosklonny MV. From causes of aging to death from COVID-19. Aging (Albany NY). 2020;12(11):10004–21. https://doi.org/10.18632/aging.103493.

Article  PubMed  PubMed Central  Google Scholar 

Powell T, Bellin E, Ehrlich AR. Older adults and Covid-19: the most vulnerable, the hardest hit. Hastings Cent Rep. 2020;50(3):61–3. https://doi.org/10.1002/hast.1136.

Article  PubMed  Google Scholar 

Ayoub HH, Chemaitelly H, Mumtaz GR, et al. Characterizing key attributes of COVID-19 transmission dynamics in China’s original outbreak: model-based estimations. Glob Epidemiol. 2020;2: 100042. https://doi.org/10.1016/j.gloepi.2020.100042.

Article  PubMed  Google Scholar 

Davies NG, Klepac P, Liu Y, et al. Age-dependent effects in the transmission and control of COVID-19 epidemics. Nat Med. 2020;26(8):1205–11. https://doi.org/10.1038/s41591-020-0962-9.

Article  CAS  PubMed  Google Scholar 

Pijls BG, Jolani S, Atherley A, et al. Demographic risk factors for COVID-19 infection, severity, ICU admission and death: a meta-analysis of 59 studies. BMJ Open. 2021;11(1): e044640. https://doi.org/10.1136/bmjopen-2020-044640.

Article  PubMed  Google Scholar 

Zhang JJ, Dong X, Liu GH, Gao YD. Risk and protective factors for COVID-19 morbidity, severity, and mortality. Clin Rev Allergy Immunol. 2023;64(1):90–107. https://doi.org/10.1007/s12016-022-08921-5.

Article  CAS  PubMed  Google Scholar 

Covid-Forecasting Team. Variation in the COVID-19 infection–fatality ratio by age, time, and geography during the pre-vaccine era: a systematic analysis. Lancet. 2022;399(10334):1469–88. https://doi.org/10.1016/S0140-6736(21)02867-1.

Article  Google Scholar 

Near AM, Tse J, Young-Xu Y, Hong DK, Reyes CM. Burden of influenza hospitalization among high-risk groups in the United States. BMC Health Serv Res. 2022;22(1):1209. https://doi.org/10.1186/s12913-022-08586-y.

Article  PubMed  PubMed Central  Google Scholar 

Centers for Disease Control and Prevention. Flu & people 65 years and older. https://www.cdc.gov/flu/highrisk/65over.htm. Accessed 16 Feb 2024.

Falsey AR, Walsh EE. Respiratory syncytial virus infection in adults. Clin Microbiol Rev. 2000;13(3):371–84. https://doi.org/10.1128/cmr.13.3.371.

Article  CAS  PubMed  PubMed Central  Google Scholar 

Savic M, Penders Y, Shi T, Branche A, Pirçon JY. Respiratory syncytial virus disease burden in adults aged 60 years and older in high-income countries: a systematic literature review and meta-analysis. Influenza Other Respir Viruses. 2023;