Chicken pox is, traditionally, temporarily uncomfortable for kids and troublesome for parents. But in some rare cases, it's much more: Varicella (chicken pox's scientific name) can lead to infections and pneumonia in otherwise healthy children and adults, and a small but significant number of people die each year.
For the study, the researchers tracked deaths by varicella since the introduction of the vaccine in 1995. In 2007, there were 14 directly varicella-related deaths in the United States, as opposed to an annual average of 105 in the four years leading up to the vaccine's introduction. In 2006, the CDC suggested that a second dose of the vaccine could completely eliminate varicella deaths in the country.