Fact sheet about chickenpox

What is chickenpox?

Chickenpox, also called varicella, is a disease caused by a virus that spreads easily from person to person.  It causes an itchy rash that looks like tiny blisters. The rash usually starts on the face, stomach, chest or back, and spreads to other parts of the body. A mild fever, tiredness, and slight body discomfort usually come with the rash. Anyone who hasn’t had chickenpox already can get it, but it is most common among children under 15 years old.  Most US adults have already had chickenpox and many children have been vaccinated.

Is chickenpox dangerous?

Yes, it can be. Chickenpox can lead to severe skin infection, scars, pneumonia, brain damage and death. Serious complications (such as pneumonia) are rare, but are more common in newborns, pregnant women, people with weak immune systems, and adults in general. Before the vaccine became available in 1995, about 11,000 people were hospitalized for chickenpox each year in the US, and about 100 people died. A person who has had chickenpox can also get a painful rash, called shingles (zoster), years later.

How is chickenpox spread?

The virus that causes chickenpox lives in the nose and throat and is sprayed into the air when an infected person sneezes, coughs or talks.  It is also in the blisters and rash. Chickenpox is spread from person to person by coughing, sneezing, or touching the rash. People with chickenpox can spread the disease from 1 – 2 days before symptoms start and until all the blisters are crusted over (usually about 5 days).  However, people with weak immune systems are contagious longer, usually as long as new blisters keep appearing. Symptoms usually appear about 10 – 21 days after exposure to the virus.

Who gets chickenpox?

  • Anyone who has never had chickenpox and has never been vaccinated.
  • Babies younger than 12 months old, because they are too young to be vaccinated.
  • Sometimes people who have had the vaccine will still get chickenpox (called ‘breakthrough disease’).  If vaccinated people do get chickenpox, it is usually very mild. They will have fewer spots, are less likely to have a fever, and will recover faster.

How can you prevent chickenpox?

  • Two doses of chickenpox vaccine are recommended to protect against disease. Protect your children by having them vaccinated when they are 12-15 months old and again at 4 to 6 years. Parents whose child has received only 1 dose of chickenpox vaccine should talk with their health care provider about a 2nd dose of chickenpox vaccine for the child, particularly if they have been in contact with someone with chickenpox.
  • Those 13 years of age and older who are not immune to chickenpox, particularly those who are health care workers or who live with someone who has a weakened immune system, should be vaccinated. They need 2 doses of chickenpox vaccine and should check with their provider about getting this vaccine.
  • Women who plan to have children and are not immune should also be vaccinated before they become pregnant.
  • If a person who is not vaccinated and hasn’t had chickenpox receives chickenpox vaccine within 3 (and possibly up to 5) days of being in contact with someone with chickenpox, there is a good chance they won’t get sick. Some people who have not had chickenpox disease or vaccine are at increased risk for complications (such as newborns, pregnant women, and people with weakened immune systems) if they get chickenpox.  They should see their doctor.
  • State regulations require certain groups be vaccinated against chickenpox. Children attending licensed child care or preschool are required to have one dose of varicella vaccine.  Beginning in the 2011 school year, children entering kindergarten, grade 7, full-time college freshmen and health science students must show proof of either receiving two doses of varicella vaccine or having a reliable proof of immunity. This requirement will apply to all children in kindergarten, grades 1-12 and college students by September of 2017. Talk to your school nurse if you have questions.
  • A reliable proof of immunity can be: documentation of two doses of varicella vaccine; laboratory evidence of immunity or laboratory confirmation of disease; birth in the US before 1980 (Note: birth before 1980 should not be considered evidence of immunity for healthcare providers, pregnant women, and in certain high risk settings); a healthcare provider diagnosis or verification of history of chickenpox; or history of shingles.
  • Under state regulations, people with chickenpox must stay out of school and work until all their blisters have dried and crusted.

Should pregnant women worry about chickenpox?

Pregnant women who have already had chickenpox disease or the vaccine do not need to worry. However, women who are not immune, who get chickenpox while they are pregnant, are more likely than other adults to develop serious complications. The unborn baby can also be affected.  Babies born to mothers with a current case of chickenpox can develop high fevers and other serious problems. Pregnant women who have been exposed to somebody with chickenpox should contact their doctor immediately.  Those who are not sure if they had chickenpox can have a blood test to see if they are protected against the virus.

Can you get chickenpox more than once?

Yes, but it is not common. In most cases, once you have had chickenpox, you cannot get it again. However, the virus that causes chickenpox stays in your body the rest of your life.  Years later it can give you a rash called shingles, which doctors call “herpes zoster.” The shingles rash looks like chickenpox, but it usually shows up on only one part of your body and does not spread. Unlike chickenpox, shingles is painful. Children sometimes get shingles, but it is more common among adults. Touching fluid from the shingles rash can spread the virus and cause chickenpox in people who are not immune.

Is chickenpox vaccine safe?

Yes, it is safe for most people. However, a vaccine, like any medicine, is capable of causing problems like fever, mild rash, temporary pain or stiffness in the joints, and allergic reactions. More severe problems are very rare.  About 70– 90% of people who get the vaccine are protected from chickenpox.

Who should not get chickenpox vaccine?

  • People who have serious allergies to gelatin, the drug neomycin, or a previous dose of the vaccine should not get the vaccine
  • Pregnant women should not get varicella vaccine until after they deliver their babies
  • People with cancer, HIV, or other problems that weaken the immune system should check with their doctor or nurse before being vaccinated
  • People who recently had a blood transfusion or were given other blood products should ask their doctor when they can get chickenpox vaccine
  • People with high fevers should not be vaccinated until after the fever and other symptoms are gone

    Where can I get more information?

    • Your doctor, nurse or clinic, or your local board of health (listed in the phone book under local government).
    • The Massachusetts Department of Public Health, Immunization Program (617) 983-6800, or on the DPH website.
    • Boston healthcare providers and residents may also call the Boston Public Health Commission at (617) 534-5611.
    • CDC National Immunization Information Hotline 24 Hours/Day:
      CDC-INFO: (800) 232-4636
      TTY: (888) 232-6348
      E-mail Address:

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