Zostavax is a vaccine that is available as a powder and solvent to be made up into a solution for injection. The active substance is the attenuated (weakened) varicella-zoster virus.
|Table of Contents|
|What is it used for?|
|How is it used?|
|How does it work?|
|How has it been studied?|
|What benefits has it shown during the studies?|
|What is the risk associated?|
|Why has it been approved?|
Zostavax is used to vaccinate people aged 50 years or older, to prevent herpes zoster (also known as zoster or shingles) and the long-lasting nerve pain that may follow the disease (post-herpetic neuralgia).
The vaccine can only be obtained with a prescription.
Zostavax is given as a single dose injected under the skin, preferably around the shoulder.
Herpes zoster, or shingles, is a disease caused by the varicella-zoster virus, the same virus that causes chickenpox. Shingles develops in people who have had chickenpox earlier in life, generally as a child. After chickenpox, the varicella-zoster virus stays in the body, in the nervous system, in a ?dormant? (inactive) state. Sometimes, after many years, and for reasons which are not fully understood, the virus becomes active again, and the patient develops shingles, a painful, blistering rash typically in one part of the body. The rash takes usually several weeks to clear, and may be followed by severe long-lasting pain (post-herpetic neuralgia) in the area where the rash was.
The risk of developing shingles seems to be linked to a decline in the specific immunity (protection) against varicella-zoster virus. Zostavax is a vaccine that was shown to ?boost? this specific immunity, protecting against shingles and the pain associated with it.
The main study of Zostavax compared the vaccine with placebo (a dummy vaccine) in around 39,000 patients aged between 59 and 99 years. The study was a double-blind trial, which means that neither the doctor nor the patient knew what treatment the patient was receiving. The patients were followed for 2 to 4.5 years after vaccination. The main measure of effectiveness was based on the number of people who developed shingles and post-herpetic pain.
Two further studies looked at Zostavax in over 1,000 patients aged 50 years or older, of whom 389 were between 50 and 59 years of age. The studies looked at the ability of the vaccine to stimulate the production of antibodies against varicella-zoster virus in the blood, four weeks after injection.
Zostavax was more effective than placebo in preventing shingles. Fewer people developed shingles after vaccination with Zostavax than placebo: 315 of the 19,254 patients who received Zostavax had shingles during the study, compared with 642 of the 19,247 who received placebo. Zostavax was also more effective than placebo in preventing post-herpetic neuralgia: 27 of the Zostavax patients had post-herpetic neuralgia, compared with 80 in the placebo group.
The additional two studies showed that patients vaccinated with Zostavax had blood levels of antibodies against varicella-zoster virus that were about two to three time higher four weeks after vaccination. The effect was seen both in patients aged between 50 and 59 years and in those aged 60 years and older.
In studies, the most common side effects with Zostavax (seen in more than 1 patient in 10) are reactions at the site of the injection (redness, pain, swelling, itching, warmth and bruising). For the full list of all side effects reported with Zostavax, see the package leaflet.
Zostavax should not be used in people who may be hypersensitive (allergic) to any of the ingredients of the vaccine, including neomycin (an antibiotic). The vaccine must not be used in people who have problems with their immune system, either because they have a disease such as leukaemia, lymphoma, acquired immune deficiency syndrome (AIDS),, or because they are taking medicines that affect the immune system. It must also not be used in patients with active untreated tuberculosis or in pregnant women. For the full list of restrictions, see the package leaflet.