In 2014, the United States has experienced an increase in measles activity, the most since the elimination of the virus in 2000. The measles infection occurs in unvaccinated individuals. Communities and individuals choose to not vaccinate for a number of reasons, primarily citing religious and philosophical motives. Objections based upon religion most often center on the use of aborted human fetus tissue used in the rubella component of the combined vaccine products, and animal derived gelatins used in vaccine production. Objections among religious communities may also not be faith based, rather in some cases concerns related to lack of safety and efficacy of the vaccination result in refusal.