Shingles (herpes zoster) is no fun. It usually begins with a couple of days of pain, then a painful rash breaks out and lasts a couple of weeks. The rash consists of blisters that eventually break open, crust over, and consolidate into an ugly plaque. It is localized to one side of the body and to a stripe of skin corresponding to the dermatomal distribution of a sensory nerve. Very rarely a shingles infection can lead to pneumonia, hearing problems, blindness, brain inflammation (encephalitis) or death. More commonly, patients develop postherpetic neuralgia (PHN) in the area where the rash was. The overall incidence of PHN is 20%; after the age of 60 this rises to 40%, and after age 70 it rises to 50%. It can be excruciatingly painful, resistant to treatment, and can last for years or even a lifetime.
Shingles is caused by the varicella zoster virus, the same virus that causes chickenpox. In fact, you can’t get shingles unless you’ve had chickenpox (or, rarely, chickenpox vaccine). Some of the virus hides in a dorsal root ganglion and remains dormant for years, then travels down the nerve to affect the associated area of skin. Shingles itself is not contagious, but it is possible to get chickenpox from contact with a shingles patient.
By various estimates somewhere between one out of five and one out of three Americans will get shingles in their lifetime; it’s more common after age 50 due to an age-related decline in cell-mediated immunity, and it’s more common in patients who are immunosuppressed. If you live to be 85, there is a 50% chance that you will have had shingles by then.
Since 2006, a shingles vaccine (Zostavax) has been available. It contains a live attenuated virus. It is recommended for everyone over the age of 60, even those who have already had shingles. There are a few contraindications like allergy to neomycin, immunosuppression, or contact with a pregnant woman who has not had chickenpox. But how safe is it? A new study is reassuring.
Pre-marketing tests showed that it was safe, but now a post-marketing study has expanded our knowledge. The VA did a randomized double-blind trial of Zostavax with over 38,000 subjects and followed them for 3.4 years. Serious adverse events occurred in 1.4% of patients who got the vaccine, but they also occurred in 1.4% of those who got a placebo! There was no indication that any of these reactions were actually caused by the vaccine. The incidence of minor inoculation-site effects (redness, swelling, pain and tenderness at the injection site) was higher in the vaccine (48%) than in the placebo group (16%), as would be expected.
How effective is it? Zostavax has been demonstrated to prevent 51% of shingles and 67% of postherpetic neuralgia. By one estimate, the number needed to treat (NNT) to prevent one case of shingles over a 3 year period is 58 and the NNT to prevent one case of PHN is 364. It is estimated that this vaccine could prevent 250,000 cases of shingles a year in US plus reduce the severity of the disease in another 250,000.
The public health implications of varicella vaccines are controversial. People living with children are less likely to get shingles — about 25% of cases are prevented. Apparently this is because adults are re-exposed to the virus and this boosts their immunity. As more children are vaccinated against chickenpox, this protective re-exposure effect will disappear; hence, more cases of shingles in the short term. In the long term, vaccinating children could drastically reduce the incidence of shingles in the population.
Only about 7% of eligible patients have received the vaccine. It costs around $200 and must be kept in a freezer. It’s covered under Medicare part D, but not part B.
For more information, see the CDC website.
Conclusion
Zostavax is safe and effective. Although not as effective as we could wish, it can significantly reduce the burden of a serious disease in the elderly population. It is recommended for everyone age 60 and over by the CDC and by many medical organizations like the American Academy of Family Physicians. Admittedly, the arguments for this vaccine are nowhere near as compelling as the arguments for polio, DPT and MMR vaccines for children. After learning the facts, not everyone will choose to take Zostavax. I chose to take it, and so did my husband.
This article was originally published in the Science-Based Medicine Blog.
