- Chickenpox is caused by varicella-zoster virus (VZV)
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. Approximately 4 million cases
occur in the United States each year.
- The virus spreads 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 occurs 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 his or her 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.
- 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 caused by the wild virus, which may occur in a
small proportion of vaccinees, are typically very mild, with fewer than 50 skin lesions
and no fever.
- It is recommended that all children be routinely
vaccinated at 12-18 months of age and that all susceptible children receive the vaccine
before their 13th birthday (CDC Advisory Committee on Immunization Practices, the American
Academy of Pediatrics and the American Academy of Family Physicians). 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 cancer,
human immunodeficiency virus/AIDS; those receiving medications that depress the immune
system).
- Varicella zoster immune globulin (VZIG), an immune globulin
made from plasma of healthy volunteer blood donors with high levels of antibody to VZV, 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).
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