CDC Media Relations: Facts About Chickenpox (Varicella)
Facts About Chickenpox (Varicella)
Source: Centers for Disease Control and Prevention
Chickenpox is caused by Varicella zoster virus and is usually mild, but it may be severe in infants, adults and persons with impaired immune systems. Almost everyone gets chickenpox by adulthood (more than 95% of Americans). Chickenpox is highly contagious. CDC estimates that 4 million cases occur each year.
The virus spread from person to person by direct contact, or through the air. Approximately 90% of persons in a household who have not had chickenpox will get it if exposed to an infected family member.
The greatest number of cases of chickenpox occur in the late winter and spring.
Chickenpox has a characteristic itchy rash, which then forms blisters that dry and become scabs in 4-5 days. The rash may be the first sign of illness, sometimes coupled with fever and general malaise which is usually more severe in adults. An infected person may have anywhere from only a few lesions to more than 500 lesions on their body during an attack (average 300-400).
Adults are more likely to have a more serious case of chickenpox with a higher rate of complications and death.
Chickenpox is contagious 1-2 days before the rash appears and until all blisters have formed scabs. Chickenpox develops within 10-21 days after contact with an infected person.
Every year there are approximately 5,000-9,000 hospitalizations and 100 deaths from chickenpox in the United States.
In the United States, the annual cost of caring for children of normal health who contract chickenpox was estimated as $918 million in 1993.
Varicella vaccine has been available since March 1995, and is approved for use in healthy children 12 months of age or older, and susceptible (i.e., no evidence of having had chickenpox in the past) adolescents and adults.
Varicella vaccine is highly effective in protecting against severe chickenpox. Cases of disease due to the wild virus, that may occur in a small proportion of vaccinees, are typically very mild with fewer than 50 skin lesions and no fever.
More than 6 million doses of varicella vaccine have been given since it was licensed in March 1995.
CDC’s Advisory Committee on Immunization Practices, the American Academy of Pediatrics and the American Academy of Family Physicians recommend that all children be routinely vaccinated at 12-18 months of age and that all susceptible children receive the vaccine before their 13th birthday (ACIP, AAP). The vaccine is also approved for susceptible adolescents and adults especially those with close contact with persons at high risk for serious complications (e.g., health-care workers, family contacts of immunocompromised persons).
A history of chickenpox is considered adequate evidence of immunity.
A blood test is available to test immunity in persons who are uncertain of their history or who have not had chickenpox. Many of these persons will find that they are immune when tested and thus will not need to be vaccinated.
Effective medications (e.g., acyclovir) are available to treat chickenpox in healthy and immunocompromised persons (e.g, those with cancers, HIV/AIDS, receiving medications that depress the immune system).
Varicella zoster immune globulin (VZIG), an immune globulin made from plasma from healthy, volunteer blood donors with high levels of antibody to the varicella zoster virus, is recommended after exposure for persons at high risk for complications (e.g., immunocompromised persons, pregnant women, premature infants <28 weeks gestation or < 1000 grams at birth and premature infants whose mothers are not immune).
For more information about varicella and other vaccine-preventable diseases, contact CDC’s National Immunization Hotline at 1-800-232-2522 (English) or 1-800-232-0233 (Spanish).
Centers for Disease Control and Prevention