Varicella-zoster vaccine for chicken pox
Examples
Generic Name Brand Name varicella-zoster vaccine Varivax Chicken pox (varicella) is a common contagious illness caused by a type of herpes virus. The chicken pox vaccine (varicella-zoster vaccine) is given by injection, usually into the layer of fat under your skin. It also can be injected into your muscle.
How It Works
When you receive the chicken pox vaccine, your body reacts by producing antibodies to fight against the varicella virus.
Why It Is Used
Varicella vaccine prevents chicken pox. The vaccine is recommended for all healthy children, teens, and adults who have not had chicken pox.1
- Babies can receive the vaccine along with some other standard shots (immunizations) that are given between 12 months and 18 months of age.
- Children aged 12 months through 12 years can receive the vaccine at any time.
- Healthy adolescents and young adults aged 13 and older should receive two doses of the vaccine 4 to 8 weeks apart.
- Adults who have not had chicken pox should also receive two doses of vaccine. The vaccine is especially recommended for the following adults:
- People who work in settings where they are likely to come in contact with people with chicken pox (for example, health care workers, child care workers, students in group living situations). Sometimes employers require proof of immunity to or vaccination for chicken pox.
- Non-pregnant women who can have children. Women who have not had chicken pox or the vaccine are at risk for complications of chicken pox during pregnancy.
- Family members of people with impaired immune systems. This protects them from having chicken pox and thus protects their family member who has an impaired immune system.
- People who travel outside Canada and the United States. In some countries (especially tropical countries), chicken pox is a disease of adults.
Older children, teens, and adults can receive the vaccine at any time. Some provinces now require proof that children entering daycare and school have either had chicken pox or have been vaccinated to prevent the virus.
A person who has been exposed to someone with chicken pox also can have the vaccine to prevent or decrease the severity of chicken pox. It is recommended that the vaccine be given within 3 days after exposure.
Chicken pox vaccine is not recommended for:
- Women who are pregnant or breast-feeding. Women need to wait 1 month after receiving the chicken pox vaccine before they become pregnant.
- Some people with impaired immune systems.
- People who are taking high doses of corticosteroids by mouth. People who are taking low doses or taking the medications by inhalation (such as people with asthma) may be able to take the chicken pox vaccine.
- People with serious long-term illnesses, such as children with leukemia.
- People who are allergic to the antibiotic neomycin. The chicken pox vaccine contains a small amount of neomycin.
- People who have recently received an injection of immune globulin. This medication increases the body's ability to fight infection. People need to wait for 3 to 6 months after receiving immune globulin before receiving the chicken pox vaccine.
How Well It Works
When you are given the chicken pox vaccine, your body produces antibodies against the chicken pox virus. These antibodies stay in your body and protect you just like they would if you had chicken pox. This is called immunity against chicken pox.
It is not known how long immunity from the vaccine lasts, because the vaccine has only been used in Canada since 1998. So far, people vaccinated against chicken pox since 1998 are still immune. In addition, a chicken pox vaccine given in Japan for more than 20 years still protects people against the virus.1
Varicella vaccine is safe and effective in preventing chicken pox.1
- More than 95% of healthy children who receive the vaccine between ages 12 months and 12 years develop immunity to chicken pox.
- Between 78% and 82% of people aged 13 and older who receive one dose of the vaccine are protected against chicken pox; 99% are protected after receiving two doses of the vaccine.
- The vaccine protects against moderate to severe cases of chicken pox in 95% of people immunized and against mild infection in 70% to 85%.
Occasionally chicken pox develops even in people who receive the vaccine. This is called breakthrough infection. However, if this happens, you will likely develop a mild form of the disease, with few blisters and symptoms.
Some research indicates that the chance of developing a breakthrough chicken pox infection after vaccination increases with the length of time since vaccination.2, 3 In one study, the effectiveness of the vaccine declined after the first year when given to children younger than 15 months.4 As a result of this and other studies, experts are debating whether a second vaccination, or booster, should be recommended for children younger than 13.
Side Effects
The varicella vaccine has few side effects. The number or severity of side effects does not increase if someone takes the vaccine without knowing whether he or she has had chicken pox. Side effects are usually seen more often in teens and adults than in children.
Side effects of the chicken pox vaccine include:
- Pain, redness, and swelling. About 20% of children have redness or soreness at the injection site.1
- Rash. About 3% to 5% of children develop a rash around the injection site, and an additional 3% to 5% of children develop a rash all over their body.1
- Fever. About 10% to 14% of children and 10% of teens and adults have a slight fever [37.8°C (100°F)] after receiving the vaccine.5
See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)
What To Think About
Consider the following when deciding whether to get the chicken pox vaccine for you or your child.
- Getting the vaccine prevents the spread of chicken pox.
- People who get the chicken pox vaccine are less likely to have shingles later in life than people who have had chicken pox. If vaccinated people do get shingles, symptoms are usually very mild.
- If you are not sure whether you have had chicken pox, you can have a blood test to check for antibodies against the varicella virus. If you have had chicken pox, you will have chicken pox antibodies in your blood and you don't need the vaccine.
- It is safe for healthy children and adults to get the chicken pox vaccine without knowing whether they have ever had chicken pox. The risk of side effects does not increase if you get the vaccine even though you have had chicken pox in the past.
- Getting the chicken pox vaccine may not prevent chicken pox if you were around someone with chicken pox just before (within 21 days) you received the vaccine. This is because you were infected with the chicken pox virus before you received the vaccine. However, your symptoms may be less severe.
- Some parents choose not to give their child the chicken pox vaccine. Not giving your child the vaccine significantly increases his or her chances of having chicken pox at some point, and possibly complications from chicken pox. Talk with your health professional about any questions or concerns you have about giving your child this vaccine.
- Occasionally some people develop a mild rash with a few blisters after having the chicken pox vaccine. If this occurs, you should avoid all people who are not immune to the virus until the rash is gone and all blisters have dried and crusted over. While you are contagious, you should take special care to stay away from people with impaired immune systems.
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| Author: | Douglas Dana Amy Fackler, MA Debby Golonka, MPH | Last Updated: August 25, 2006 |
| Medical Review: | Adam Husney, MD - Family Medicine Michael J. Sexton, MD - Pediatrics Thomas Emmett Francoeur, MDCM, CSPQ, FRCPC - Pediatrics | |
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| Topic Contents | |
| Examples | |
| How It Works | |
| Why It Is Used | |
| How Well It Works | |
| Side Effects | |
| What To Think About | |
| References | |