Major changes in social welfare, economic conditions and medical knowledge over the last 60 years have produced
a demographic shift in the population. More individuals are living longer, and in a decade there will be more people
over 65 than infants under 5 for the first time in history. Taking the analysis beyond mere numbers reveals that older individuals
are now physically more active than their forebears and travel more widely. This provides a greater opportunity
for encountering infectious agents which could present a considerable problem. Older individuals are more susceptible to
infection and do not respond as well as younger people to vaccination because of an age related decline in immunity, a
state which has been termed immunosenesence. This decline is not uniform and some older individuals show a greater decline
in their immune response than others. In this review we have sought to consider who are the 'at risk' individuals,
how they might best be treated and when.