Adults have a higher risk for developing complications from chickenpox than children. Those with weakened immune systems due to cancer, HIV, or another condition are also at risk. Once you’ve had chickenpox, the varicella-zoster virus stays in your nerve cells for years. It can “wake up” and become active again years later. It can lead to shingles, a condition that causes painful blisters. Fortunately, there’s a vaccine for shingles. Doctors recommend it for adults over 60.