Impact of Aging and Cytomegalovirus on Immunological Response to Influenza Vaccination and Infection

Abstract

The number of people over the age of 60 is expected to double by 2050 according to the WHO. This emphasizes the need to ensure optimized resilience to health stressors in late life. In older adults, influenza is one of the leading causes of catastrophic disability (defined as the loss of independence in daily living and self-care activities). Influenza vaccination is generally perceived to be less protective in older adults, with some studies suggesting that the humoral immune response to the vaccine is further impaired in cytomegalovirus (CMV)-seropositive older people. CMV is a β-herpes virus infection that is generally asymptomatic in healthy individuals. The majority of older adults possess serum antibodies against the virus indicating latent infection. Age-related changes in T-cell-mediated immunity are augmented by CMV infection and may be associated with more serious complications of influenza infection. This review focuses on the impact of aging and CMV on immune cell function, the response to influenza infection and vaccination, and how the current understanding of aging and CMV can be used to design a more effective influenza vaccine for older adults. It is anticipated that efforts in this field will address the public health need for improved protection against influenza in older adults, particularly with regard to the serious complications leading to loss of independence.

Seasonal influenza immunisation: Strategies for older adults

“…Both antibody‐mediated and cell‐mediated responses play roles in immunity to influenza; the former is thought to protect predominantly against acquiring influenza infection, while the latter mostly protects against severe outcomes . Amongst other factors, changes in thymus function with ageing affect both T cells and B cells, decreasing the immune responses to new antigens and memory responses to previously experienced antigens, leading to lower vaccine effectiveness against influenza‐associated illness …”

T Follicular Helper Cells and B Cell Dysfunction in Aging and HIV-1 Infection

“…There is growing interest in how latent cytomegalovirus (CMV) infections impact the outcome of vaccination [reviewed in Ref. ( 111 )]. In young adults, CMV infection is associated with elevated antibody responses to influenza vaccines.…”

The Prevention of Infections in Older Adults: Vaccination

“…Aging impairs the ability of the immune system to adequately respond to influenza vaccination and infection both in terms of humoral (antibody) and cell‐mediated responses . The magnitude of these aging‐related declines is increased in the presence of both frailty and chronic cytomegalovirus infection …”

“…14 The magnitude of these agingrelated declines is increased in the presence of both frailty 15 and chronic cytomegalovirus infection. 16,17 Available Vaccines for Older Adults Influenza vaccines may be categorized into three distinct types: inactivated influenza vaccine (IIV), recombinant influenza vaccine (RIV), and live attenuated influenza vaccine (LAIV). Standard-dose (SD), unadjuvanted, inactivated influenza vaccines are currently available in quadrivalent (IIV4) and trivalent (IIV3) formulations.…”