Many of us were probably too young to remember what having chickenpox was like. It’s probably an itchy experience we’d rather not remember, anyway. But the virus that causes chickenpox, the varicella-zoster virus, also causes the more painful condition shingles. Certain people with diseases compromising their immune systems might need to find alternative ways to prevent shingles, however, because they’re not only at an increased risk of it but also unable to get vaccinated.

A person’s risk of getting shingles increases with age, and about half of people who live to be 85 will experience it at one point in their lives, according to Mayo Clinic. After chickenpox subsides, the virus remains in the body, lying dormant near the spinal cord and brain. Not everyone will get it in old age, but those who do tend to have weakened immune systems from disease, or are taking medications or undergoing cancer treatment.

Researchers from the London School of Hygiene & Tropical Medicine looked at data of more than 144,000 patients who were diagnosed with shingles between 2000 and 2011. The average patient got shingles around 62 years old, and 60 percent of them were women. When the researchers compared the data to that of people who didn’t develop shingles, they found that shingles was 30 to 50 percent more likely to occur in people who had rheumatoid arthritis, chronic obstructive pulmonary disease, or inflammatory bowel disease. Asthma, chronic kidney disease, type 1 diabetes, and depression were also more common among those with shingles, but with a lower risk.

The results are the first step in determining if certain people should forgo shingles vaccinations and discuss alternative options with their doctors — the reason being that their immune systems might be too weak to handle a vaccine. Human immunodeficiency virus (HIV) is one such disease in which patients are not allowed vaccination because of these safety concerns.

Shingles is a more painful form of chickenpox, causing similar rashes but in a more localized area. Pain is usually the first symptom of the disease, after which an itchy rash, or blisters, may develop. Some people with shingles also go on to develop what’s known as post-herpetic neuralgia, in which the pain from the rash remains long after the rash has cleared up, sometimes as long as a few years. According to the Centers for Disease Control and Prevention (CDC), about one million people get shingles each year.