London School of Hygiene & Tropical Medicine

People at the highest risk of shingles are those with immunosuppressive conditions (such as HIV) but they are not entitled to vaccination due to safety concerns, according to research published in the BMJ.

Shingles is a common disease among older individuals which causes an acute painful rash and can lead to a complication (called postherpetic neuralgia) resulting in pain lasting from months to years that can significantly impair a person's quality of life.

Researchers from the London School of Hygiene & Tropical Medicine used data from over 144,000 UK adults diagnosed with shingles between 2000 and 2011, and compared this with a group of patients without shingles, to explore whether patients with certain medical conditions may be at increased risk of developing shingles.

Those at the highest risk of shingles were patients with conditions causing severe immunosuppression (such as HIV and leukaemia). For example, patients with HIV were five times as likely to develop shingles compared to individuals without HIV. Such patients are currently not eligible for vaccination due to safety concerns.

Lead author Harriet Forbes from the London School of Hygiene & Tropical Medicine said: "This study has highlighted that patients arguably most in need of protection against shingles cannot currently benefit from vaccination.  The vaccine is live and there are concerns that giving it to patients with severe immunosuppression may cause a shingles episode. Alternative risk reduction strategies among these patients, for example the use of alternative vaccines, would help those at greatest risk of this disease and its complications."

A number of relatively common conditions were also associated with an increased risk of shingles compared to individuals without these conditions. These included rheumatoid arthritis (46% increased risk), inflammatory bowel disease (36% increased risk) and chronic obstructive pulmonary disease (32% increased risk). Other common medical conditions which were associated with a smaller increase in shingles risk were asthma, chronic kidney disease, type 1 diabetes and depression.

Among those with some of these medical conditions the increased risk of shingles appeared to be greater among younger individuals. But because shingles is less common in younger individuals their absolute risk of developing shingles remains low.

The shingles vaccine is currently licensed among individuals aged over 50. The study says that further research would be required to establish whether vaccination is warranted in patients with these medical conditions, particularly those in younger age groups who are not currently targeted to receive the vaccine, but who are also less likely to develop long-term pain and complications from shingles.

The authors caution that the study findings may be an artefact, as regular visits to the doctor for a chronic condition such as diabetes may increase the chance of receiving a shingles diagnosis. However, the authors think this is unlikely as the majority of shingles patients would present to their doctor, due to the extensive rash and considerable pain associated with shingles, and free general practice attendance in the UK.

The study used a case control study design. The risk increases were calculated using conditional logistic regression to derive odds ratios for the conditions of interest, by comparing exposures in cases and their matched controls. It is therefore not possible to state absolute risk values for conditions of interest.

The research was funded by the National Institute for Health Research.

Publication

• Harriet J Forbes, Krishnan Bhaskaran, Sara L Thomas, Liam Smeeth, Tim Clayton, Sinéad M Langan. Quantification of risk factors for herpes zoster: population based case-control study. BMJ. DOI: 10.1136/bmj.g2911

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