you die from it if you get it while you're really young or really old. The mortality rate grows the older you get though cus it can turn into shingles. Best to get it anywhere between the ages of 1-14.
cdc.gov/vaccines/pubs/pinkbook/varicella.html#:~:text=The%20fatality%20rate%20for%20varicella,per%20100%2C000%20cases%20among%20adults.