Zostavax® is a vaccine that helps reduce the risk of developing shingles in older adults. This vaccine is referred to as a live vaccine because it contains a weaker version of the virus that causes shingles to allow the vaccinated individual to develop immunity. Zostavax® contains a weak form of the herpes zoster virus, which is the virus responsible for both chickenpox and shingles.
In some cases, the virus that causes chickenpox remains harmlessly in the body long after the symptoms of chickenpox have passed. This is known as dormancy. For a reason that is not completely understood, this virus may resurface and become active again, usually in people who are 60 or older. This is probably related to the fact that the strength of the immune system tends to decrease with increasing age.
Shingles refer to a frequently painful rash or outbreak of blisters on the skin. People who develop shingles are at further risk of developing post herpetic neuralgia (PHN). This condition is characterized by chronic pain that lasts after the rash associated with shingles has gone away. In some cases, the pain can last for years.
Zostavax® is recommended for people who are 60 or older and who have previously had chickenpox. Clinical trials suggest that this vaccine is most effective at preventing shingles in people who are approximately 60-70 years of age, and the vaccine was slightly less effective in people between 71-80 years of age. It was only about 15% effective in people over age 80.
People who have lowered immune function should not get the Zostavax® vaccine because it contains a weak form of the chickenpox virus, which may be dangerous to a poorly functioning immune system. A weakened immune system may result from a condition such as HIV, or immunosuppressant medications that are commonly used to treat autoimmune diseases, or from certain cancer treatments. Additionally, people who have been vaccinated may want to avoid close contact with pregnant women, infants, or people with impaired immune function for a certain period of time following the vaccination.
The side effects from Zostavax® appear to be relatively mild in people with good general health. Most commonly, there might be some swelling or redness at the site of injection. Less common side effects can include an itchy rash of the skin near the injection, headaches, or painful joints. Rare side effects can include a full allergic reaction such as difficultly breathing, the sudden onset of flu-like symptoms, or anaphylactic shock.