CDC  MMWR August 28, 2015 / 64(33);889-896 – “Since 1994, the National Immunization Survey (NIS) has monitored vaccination coverage among U.S. children aged 19–35 months. This report presents national, regional, state, and selected local area vaccination coverage estimates for children born from January 2011 through May 2013, based on data from the 2014 NIS.”