With all due respect some of your information is misleading.

CDC

Why is a higher dose vaccine available for adults 65 and older?
Human immune defenses become weaker with age, which places older people at greater risk of severe illness from influenza. Also, ageing decreases the body's ability to have a good immune response after getting influenza vaccine. A higher dose of antigen in the vaccine is supposed to give older people a better immune response, and therefore, better protection against flu.

Linkout: http://www.cdc.gov/flu/protect/vaccine/qa_fluzone.htm