In May 2006, the Food and Drug Administration approved a vaccine, known as Zostavax, to prevent shingles in adults over 60. According to the National Institute of Neurological Disorders and Stroke, the shingles vaccine reduces the risk of developing shingles by half and reduces the risk of the most common complication of shingles, a chronic pain syndrome known as post-herpetic neuralgia, by more than two-thirds. In the May 4, 2010 edition of "Annals of Internal Medicine," New York University infectious disease specialist Michael S. Simberkoff, M.D., and other members of the Shingles Prevention Study Group report that rash is the most common side effect of the shingles vaccine.
Patients who participated in the study developed two types of rashes, according to Simberkoff. The first type of rash consisted of a small number of blisters similar to shingles that developed at the injection site and did not spread. The second type of rash consisted of blisters similar to shingles that developed on a part of the body other than the injection site. These blisters, say Simberkoff and colleagues, tended to be more numerous and affected a larger area of skin, similar to naturally occuring shingles.
Patients were asked to report all rashes that developed within 42 days of receiving the shingles vaccine. Patients who experienced injection site rashes developed them sooner—two to three days after receiving the vaccine, on average-- than patients who experienced rashes elsewhere on the body, which typically appeared more than two weeks after vaccine administration.
Rashes that occurred at the injection site resolved, on average, within 5 days compared to 18 days for rashes that occurred elsewhere on the body, according to the Shingles Prevention Study Group. Rashes that occurred elsewhere likely reflected vaccine failure, rather than a side effect of vaccination. In all but a few patients, laboratory tests confirmed that the cause of the rashes was, in fact, shingles, but not the strain of the virus that was used in the vaccine.
According to the FDA, less than 1 percent of patients who received the vaccine developed a rash. Rashes occurred slightly more often—0.7 percent versus 0.1 percent—in people who received the vaccine, compared to people who received a placebo, suggesting that rash is, in fact, a side effect of the vaccine. Rashes were also more common in younger—60- to 69-year-old—patients compared to patients over 70.
In rare cases, a rash after the shingles vaccine may signal a complication, such as an allergic reaction or an infection. Symptoms of an allergic reaction, according to MedlinePlus, include chest pain or tightness, nausea, vomiting, diarrhea, breathing or swallowing problems, facial flushing or swelling, dizziness, anxiety, fear or apprehension. Symptoms of infection include injection site discharge or fever. Patients who experience these symptoms should contact their doctors for instructions or go to the emergency room.