to cause toxic effects. Thimerosal was used as a preservative to prevent the growth of bacteria and fungi in vials that contain more than one dose of a vaccine. This helps reduce the risk of potential infections or serious illness that could occur from contamination of a vaccine vial. Although there was a small increase in risk of injection site redness and swelling with vaccines containing thimerosal, there was no increased risk of serious harm or autism. Even though evidence supports the safety and efficacy of thimerosal in vaccines, thimerosal was removed from childhood vaccines in the United States in 2001 as a precaution. Monitoring The administration protocols, efficacy, and adverse events of vaccines are monitored by organizations of the US federal government, including the CDC and FDA, and independent agencies are constantly re-evaluating vaccine practices. As with all medications, vaccine use is determined by public health research, surveillance, and reporting to governments and the public. Usage The World Health Organization (WHO) has estimated that vaccination prevents 3.5–5 million deaths per year, and up to 1.5 million children die each year due to diseases that could have been prevented by vaccination. They estimate that 29% of deaths of children under five-years-old in 2013 were vaccine preventable. In other developing parts of the world, they are faced with the challenge of having a decreased availability of resources and vaccinations. Countries such as those in Sub-Saharan Africa cannot afford to provide the full range of childhood vaccinations. United States Vaccines have led to major decreases in the prevalence of infectious diseases in the United States. In 2007, studies regarding the effectiveness of vaccines on mortality or morbidity rates of those exposed to various diseases have shown almost 100% decreases in death rates, and about a 90% decrease in exposure rates. This has allowed specific organizations and states to adopt standards for recommended early childhood vaccinations. Lower income families who are unable to otherwise afford vaccinations are supported by these organizations and specific government laws. The Vaccines for Children Program and the Social Security Act are two major players in supporting lower socioeconomic groups. In 2000, the CDC declared that measles had been eliminated in the US (defined as no disease transmission for 12 continuous months). However, with the growing anti-vaccine movement, the US has seen a resurgence of certain vaccine-preventable diseases. The measles virus has now lost its elimination status in the