There can be serious complications of adult chickenpox that older people do need to worry about such as pneumonia, sepsis, encephalitis, (and pregnancy complications and birth defects for younger women)... It also gives protection against shingles for those who’ve definitely never had chickenpox. I got the shingles vaccine after seeing how painful it was for others, plus shingles can have serious complications too. One of the people I knew with it was being watched carefully for serious eye problems but fortunately it didn’t occur. It’s NOT a benign virus!