For much of the twentieth century, contracting measles, mumps, and rubella (German measles) was a common occurrence with most youngsters falling ill with each virus during childhood. While generally milder than the viral infections in the preceding chapters, all three of these diseases could have serious complications, including death. With millions of cases occurring around the world each year these diseases collectively produce significant morbidity and mortality, primarily in children. Fortunately, the second half of the twentieth century saw the development of effective vaccines against each of these viruses with a dramatic reduction in cases, serious clinical complications, and fatalities. Ultimately the three separate vaccines were combined into a single dose known as the trivalent MMR (measles/mumps/rubella) vaccine to facilitate distribution and reduce the number of shots needed. However, before detailing the science and history behind the development of each individual vaccine in the MMR injection, it is necessary to review an ugly episode in vaccine science. In 1998, Dr. Andrew Wakefield and colleagues published a fraudulent study implying that the MMR vaccine was associated with an increased risk for autism (Wakefield et al. 1998). Perhaps no vaccine has suffered more unjustly than the MMR vaccine due to Wakefield’s spurious accusation. While convincingly disproven and discredited over the subsequent decade, Wakefield’s premise created enormous and undeserved public distrust in vaccines that still resonates today, not only for the MMR vaccine but for vaccines in general.