We are in an era of intense change in the exploration and understanding of the complexity of the human microbiome and the ecosystems that surround us. While we are host to a myriad of microorganisms that have assembled into complex communities outnumbering the human body by a factor of 10-fold.  These organisms provide many of the building blocks for shared immunity in our body. The induction of host protective immunity is an important factor in the immunization against potentially fatal disease and emerging illnesses in U.S and global populations especially among immunologically susceptible naïve hosts. As described by Younger (pdf) The induction of host protective immunity is an important factor in the immunization against potentially fatal disease and emerging illnesses in U.S and global populations especially among immunologically susceptible naïve hosts.  

The past decade has witnessed a substantial decline in cases, hospitalizations, mortality and health-care costs due to vaccine-preventable illness, with new ones introduced covering a variety of new infectious challenges. The combined achievements in vaccine-preventable diseases have mirrored modifications in the public health system. These have included the greater capacity of epidemiologic studies and period health surveys, and improved methods of data collection that evolved from simple measures of disease prevalence to complex studies of precise analysis available in cohort, case-control, and randomized clinical trials to establish the efficacy of vaccination and demonstrate its relatively low risk. The Centers for Disease Control and Prevention (CDC) assumes responsibility for collecting and publishing notifiable diseases and tracks more than 52 infectious illnesses.  Public health efforts enjoining federal, state, county, local governmental health departments and nongovernmental organizations need to interact effectively to track infectious illness in the U.S. and rates of childhood vaccination.  
 
Vaccination as a method of disease prevention is widely accepted globally. Goal 4 of the United Nations Millennium Development Goals (MDG) to reduce childhood mortality focuses on the delivery of effective vaccinations for children under the age of 5 years.  Measles vaccination prevented nearly 15.6 million deaths worldwide between 2000 and 2013. The number of globally reported measles cases declined by 67% during the same period, with 84% of children worldwide receiving at least one dose of measles containing vaccine in 2013 up 73% from 2000. Chasing a disease down to the last few cases in underdeveloped countries to levels of the developed world remains a challenge.   While most of the record decline of childhood infectious disease is attributable to increase in the use of vaccines, a small but significant minority of parents in the U.S. oppose the use of vaccines on children. In that regard, the lay public should continue to voice their opinions guided by the scientific community in support of necessary vaccinations, leaving aside ones with intolerable side effects such as the Lymerix vaccine, which was voluntarily withdrawn after demonstrating adverse neurological sequela. Even a 1 in a million anticipated severe neurological side effect from influenza vaccination should lead the scientific community to continue to strive to develop more effective and safer approaches to vaccination.