Varicella Disease(Chickenpox)

1. What is varicella (chickenpox)?

Chickenpox is an infectious disease caused by the varicella-zoster virus which results in a blister-like rash, itching, tiredness and fever.

The rash appears first on the trunk and face, but can spread over the entire body causing between 250 to 500 itchy blisters. Most cases of chickenpox occur in persons less than 15 years old. Prior to the use of varicella vaccine, the disease had annual cycles, peaking in the spring of each year.

2. How do you get chickenpox?

Chickenpox is highly infectious and spreads from person to person by direct contact or through the air from an infected personís coughing or sneezing. A persons with chickenpox is contagious 1-2 days before the rash appears and until all blisters have formed scabs. It takes from 10-21 days after contact with an infected person for someone to develop chickenpox.

3. What is the chickenpox illness like?

In children, chickenpox most commonly causes an illness that lasts about 5-10 days. Children usually miss 5 or 6 days of school or childcare due to their chickenpox. About half of all children with chickenpox visit a health care provider due to symptoms of their illness such as high fever, severe itching, an uncomfortable rash, dehydration or headache. In addition, about 1 child in 10 has a complication from chickenpox serious enough to visit a health care provider including infected skin lesions, other infections, dehydration from vomiting or diarrhea, exacerbation of asthma or more serious complications such as pneumonia.

Certain groups of persons are more likely to have more serious illness with complications. These include adults, infants, adolescents and people with weak immune systems from either illnesses or from medications such a long-term steroids.

4. What are the serious complications from chickenpox?


Serious complications from chickenpox include bacterial infections which can involve many sites of the body including the skin, tissues under the skin, bone, lungs (pneumonia), joints and the blood. Other serious complications are due directly to the virus infection and include viral pneumonia, bleeding problems and infection of the brain (encephalitis). Many people are not aware that, before a vaccine was available, there were approximately 11,000 hospitalizations and 100 deaths from chickenpox in the U.S. every year . One child and one adult died each week.

5. Can a healthy person with varicella die from the disease?

Yes, many of the deaths and complications from chickenpox occur in previously healthy children and adults. From 1990 to 1994, before there was a vaccine available, there were about 50 chickenpox deaths in children and 50 chickenpox deaths in adults every year; most of these persons were healthy or did not have a medical illness (such as cancer) that placed them at higher risk of getting severe chickenpox. Since 1999, states have been encouraged to report chickenpox deaths to CDC. In 1999 and 2000, CDC received reports that showed that deaths from chickenpox continue to occur in healthy, unvaccinated children and adults. Most of the healthy adults who died from chickenpox contracted the disease from their unvaccinated children.

6. Can chickenpox be prevented?

Yes, chickenpox can now be prevented by vaccination. See Chickenpox Vaccine for more details about who should and should not receive a vaccine.

7. Can you get chickenpox more than once?

Yes, but it is uncommon to do so. For most people, one infection is thought to confer lifelong immunity.

8. Chickenpox in children is usually not serious. Why not let children get the disease?

This public health strategy ignores the fact that more than 90% of cases, approximately 60% of hospitalizations and 40% of deaths due to varicella occur in children less than 10 years of age. The majority of this morbidity is preventable by vaccination. In addition, children miss an average of 5-6 days of school when they have varicella and caregivers miss 3-4 days of work to care for their sick children. The majority of adults who acquire varicella, as well as persons at high risk for severe disease who are not eligible for vaccination, contract the disease from unvaccinated children. Cost-benefit studies have demonstrated that when societal costs are considered as well as direct medical costs, $5.40 is saved for every $1.00 spent on varicella vaccination in children. Experience with vaccination programs both in the U.S. and elsewhere, has consistently demonstrated that childhood vaccination programs are much more successful than those aimed at adolescents and adults. Finally, it is not possible to predict which child (or adult) will suffer serious complications from varicella. Now that a safe and effective vaccine is available, it is not worth taking this risk.

9. What is "breakthrough" disease?

A breakthrough infection is defined as a case of wild-type varicella that occurs more than 42 days after vaccination following exposure to wild-type virus. A breakthrough infection is usually very mild with mild or no fever; patients typically develop fewer than 50 skin lesions and experience a shorter duration of illness than those with natural infection who were not vaccinated. Breakthrough rate is estimated to be approximately 2% of vaccines per year and does not appear to increase with length of time since vaccination.

10. How transmissible is a varicella breakthrough infection?

One study of transmission in a household setting indicated that the risk of transmission is similar to that following natural disease. Some experts speculate that given a shorter duration of illness and with fewer skin lesions and vesicles, it might be assumed that transmission is lower from breakthrough disease than from natural disease. Further studies of this issue are needed.

11. Herpes zoster (shingles) related:

Can someone who has been vaccinated for varicella later develop herpes zoster from the vaccine virus?

Yes. See Shingles for more information. The VAERS rate of herpes zoster after varicella vaccination was 2.6/100,000 vaccine doses distributed (CDC, unpublished data, 1998). The incidence of herpes zoster after natural varicella infection among healthy children aged less than 20 years is 68/100,000 person years and, for all ages, 215/100,000 person years. However, these rates should be compared cautiously because the latter rates are based on populations monitored for longer time periods than were the vaccinees. For PCR-confirmed herpes zoster cases, the range of onset was 25-722 days after vaccination (Merck and Company, Inc., unpublished data, 1998). Cases of herpes zoster have been confirmed by PCR to be caused by both vaccine virus and wild-type virus, suggesting that some herpes zoster cases in vaccinees might result from antecedent natural varicella infection (Merck and Company, Inc., unpublished data, 1998).

Can boosting of immunity through vaccination prevent herpes zoster?

Phase I and II studies involving 400-500 adults over 55 years of age have shown that the vaccine boosts humoral and cellular immunity. A clinical trial, that will ultimately enroll 30,000 adults, is now underway to test a newly formulated varicella vaccine in adults > 55 years of age with a prior history of varicella. Three to five year follow-up will assess both the risk and the severity of herpes zoster in this cohort. See Shingles Vaccine for more information about the Shingles vaccine.

12. Acyclovir treatment related:

When is oral acyclovir treatment appropriate for someone with varicella?

Oral acyclovir therapy is not routinely recommended by the AAP for otherwise healthy children experiencing uncomplicated cases of varicella. Certain groups at increased risk of developing severe disease should be considered for oral acyclovir therapy. These high risk groups include: healthy, nonpregnant persons 13 years and older; children older than 12 months with chronic cutaneous or pulmonary disorder and those receiving long-term salicylate therapy; children receiving short, intermittent or aerosolized courses of corticosteroids (data are lacking but acyclovir may be considered for this group); some physicians may elect to use oral acyclovir for secondary cases within a household.

For maximum benefit, oral acyclovir therapy should be initiated within the first 24 hours after rash onset.

When is intravenous acyclovir treatment appropriate for someone with varicella?

Intravenous acyclovir therapy is recommended for the treatment of primary varicella or recurrent zoster in the immunocompromised child and for viral-meditated complications (e.g., pneumonia) of varicella in the normal host.