Chicken Pox

What is chicken pox?

Chicken pox is a highly contagious disease that is caused by the varicella virus, a member of the herpes virus family. In temperate climates, chickenpox occurs most frequently in winter and early spring. It is common in the United States and worldwide. Virtually everyone who is not vaccinated acquires chickenpox by adulthood. The disease is usually more severe if acquired as an adult.


How is chicken pox transmitted?

Chicken pox is spread easily to others by direct person-to-person contact, by droplet or airborne spread of discharges from an infected person's nose and throat or indirectly by contact with articles freshly soiled by discharges from the infected person's lesions. The scabs themselves are not considered infectious.

How long can a person be contagious?

An infected person is most contagious from one to two days before the onset of rash until all lesions have crusted. People who are immunocompromised may be contagious for a longer period of time. The symptoms may appear any time between 10-21 days (but usually 14-16 days) after exposure to someone with chickenpox.

What are the symptoms of chicken pox?

Initial symptoms include sudden onset of mild fever and feeling tired and weak. These are soon followed by an itchy blister-like rash which appear in 3 or more successive waves. The blisters tend to be more common on covered than on exposed parts of the body. They may appear on the scalp, armpits, trunk and even on the eyelids and in the mouth. The blisters eventually dry, crust over and form scabs by 2-3 weeks from the onset of disease

Are there any complications to getting the disease?

Rarely the condition may be fatal particularly when it occurs in adults or persons with impaired immunity. The varicella virus can cause viral pneumonia and encephalitis (infection of the brain). A more common complication is infection of the blisters if they are scratched.

Once the virus invades the body, it lives in a sensory nerve ending quietly. However, under certain circumstances the virus can reactivate and multiply causing a severe blistering painful rash called shingles. The pain known as postherpetic neuralgia can last months to even years.

Also aspirin or aspirin containing products should never be given if chicken pox is suspected in children. It has been associated with a serious illness called Reyes Syndrome which can affect the liver and the brain and cause death.

Why is chickenpox a concern during pregnancy?

Most pregnant women are immune and are not at high risk. However a non-immune pregnant woman is at risk for chicken pox pneumonia which may occur in 10% of the cases and which can be life threatening.

If the exposure occurs during the first half of the pregnancy then there is a higher risk for birth defects to the child. This condition is characterized by skin scarring, malformed limbs, an abnormally small head, vision or hearing problems, and motor or mental developmental disabilities.

If the exposure occurs toward the end of pregnancy, between five days before giving birth, or two days after delivery, then the baby has a 30 to 40 percent chance of developing what's called neonatal varicella which can be life threatening, especially if left untreated. Fortunately, the risk of a severe case can be reduced if the baby is given a shot of varicella zoster immune globulin (VZIG), a blood product that contains chicken pox antibodies.

Does a past infection with chicken pox protect you from getting the disease again?
Chickenpox generally results in lifelong immunity. However, this infection may remain hidden and recur years later as shingles in a proportion of older adults and sometimes in children.

How can immunity be checked?

A simple blood test can be done to check the level of the antibodies present. The test may cost about $100.00 and it may not be covered by insurance.

What are the recommendations for the chicken pox vaccine?

The Advisory Committee on Immunization Practices (ACIP) recommends vaccination for chicken pox. For children under 13 years, two doses of vaccine are recommended. The first dose should be administered at 12 – 15 months of age and the second dose at 4 – 6 years of age. A second dose of catch-up varicella vaccination is recommended for children, adolescents, and adults who previously had received one dose. For anyone 13 years or older who has not had the disease, two doses of vaccine are recommended at an interval of 4-8 weeks. In case of uncertainty, prior varicella disease is not a contraindication to varicella vaccination.

Individuals who should not get the varicella vaccine include children with leukemia or other cancers, people whose immune systems may be weakened due to disease or medications, people taking high doses of steroid medications, pregnant women, and infants younger than 1 year.

How effective is the vaccine?

The vaccine is about 80% effective after the first dose and 99% effective after the second dose. Vaccine-induced immunity is believed to be long lasting.

Since the vaccine is not 100% effective, a modified varicella, known as breakthrough disease, can occur in some vaccinated persons. Breakthrough disease is most commonly (~ 70% - 80% of cases) mild, with fewer than 50 skin lesions, no fever and shorter duration of rash. . The breakthrough varicella is contagious and cases should be isolated for as long as lesions persist.

Administration of the vaccine to individuals within 72 hours of the disease may prevent or significantly reduce the severity of the disease.

What are the side effects of the vaccine?

The most common side effects are injection site complaints such as pain, soreness, redness, and swelling. A localized rash may also occur at that site. A generalized rash with a small number of lesions may rarely occur, within 3 weeks of vaccination. Fever may occur in 10-15% of the patients.

Varicella vaccine is a live-virus vaccine and results in a latent infection similar to that caused by wild varicella virus. Consequently, shingles caused by the vaccine virus has been reported. This appears to occur at a lower rate than following natural infection.

Women who have received the vaccine should not become pregnant for one month after the vaccination.

Can chicken pox be treated?

Acycolvir and other antiviral medications have been used to treat some individuals. In general they are not recommended for treating children since the disease is milder in children.

Oatmeal baths can help relieve itching.

Acetaminophen can be used to treat fever.