The percentage of adults aged 65 and over who had ever

...received a pneumococcal vaccination increased from 42.4% in 1997 to 53.1% in 2000, and then increased more slowly to 63.7% in January–March 2015.

Source: "Early Release of Selected Estimates Based on Data From the January–March 2015 National Health Interview Survey," National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention, September 2015, http://www.cdc.gov/nchs/data/nhis/earlyrelease/earlyrelease201509.pdf