Facts About Chickenpox (Varicella)
May 16, 1997
- 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 45 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 300400).
- Adults are more likely to have a more serious case of chickenpox with a higher
rate of complications and death.
- Chickenpox is contagious 12 days before the rash appears and until all blisters
have formed scabs. Chickenpox develops within 1021 days after contact with
an infected person.
- Every year there are approximately 5,0009,000 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 1218 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.,
healthcare 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 vaccinepreventable diseases, contact CDC's
National Immunization Hotline at 18002322522 (English) or 18002320233 (Spanish).
|