Annals of Clinical Trials and Vaccines Research

Aging And Immunization

 There is much evidence for the decline in function of the immune system with age, termed immunesenescence. The role of the immune system is 3-fold: to protect the host from pathogens; to recognize “altered cells” such as cancers; and to do both of these things while not reacting to self-antigens. With aging each of these arms of the immune system is compromised. In relation to protection from infection, the incidence of bacterial infections such as the hospital superbugs Clostridum difficile and Methicillin-resistant staphylococcus aureus (MRSA) is highest in people aged over 75 y and bacterial infections such as pneumonia are not only more frequent in the over 65s but the patients have much higher mortality. Detection and elimination of tumors is also reduced as cancer incidence increases with age for most cancers. The immune system is also less tolerant of self and several autoimmune conditions such as Rheumatoid arthritis have a peak age of onset in late middle age. Another key element of the immune system is the ability to generate immune memory, allowing the host to produce a more rapid and specific response to the pathogen when encountered for a second time. This aspect of immunity is of course also the basis of vaccinations. Vaccination is an important prophylactic measure against infections but the response to vaccination in terms of the titer, efficacy and affinity of antibody produced has also been shown to diminish with aging. One study in rhesus monkeys demonstrated immunesenescence in old and very old monkeys, for example reduced antibody response to influenza vaccination was noted.  

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