Severity of chickenpox in adults

Adult deaths from chickenpox

These cases illustrate that varicella is potentially fatal. Although fewer than 5% of cases occur in people over age 20, 55% of varicella-related deaths occur in this age group.

The Chickenpox Vaccine:  What Parents Need to Know - American Academy of Pediatrics

Most healthy children who get chickenpox won't have any complications from the disease.  However, each year in the United States around 9,000 people are hospitalized for chickenpox and about 90 people die from the disease.

Before the vaccine became available, there were about 4 million cases of chickenpox in the United States each year.

(Note:  This works out to around 2.25 hospitalizations per 1,000 cases and 2.25 deaths per 100,000 cases.  It also begs the question - how many of these were adults and how many of these were mismanaged?)

When an adult gets the chickenpox, it is usually more severe, often developing into pneumonia. Adults are 10 times more likely to be hospitalized for chickenpox than children under 14 years of age, and adults are more than 20 times more likely to die from the disease.