General questions:

1. How serious a disease is varicella?
2. What complications can result from varicella?
3. Why vaccinate children for what is usually a benign disease? Why not allow children to acquire natural infection and offer vaccine only to susceptible adolescents and adults?
4. What is "breakthrough" disease?
5. How transmissible is a varicella breakthrough infection?

Herpes zoster (shingles) related:

1. Can someone later develop herpes zoster from varicella vaccine?
2. Can boosting of immunity prevent herpes zoster?

Acyclovir treatment related:

1. When is oral acyclovir treatment appropriate?
2. When is intravenous acyclovir treatment appropriate?

Go to other pages of related questions:

• Vaccine specific
• Health care workers related
• Who should get vaccinated
• Pregnancy related

Varicella
How serious a disease is varicella?
	Prior to the availability of varicella vaccine there were approximately 4 million cases of varicella a year in the U.S. Although varicella is frequently perceived as a disease that does not cause serious illness, especially among healthy children, many health care providers are not aware that 11,000 hospitalizations and 100 deaths occurred every year in the United States before varicella vaccine became available. The majority of deaths and complications occurred in previously healthy individuals.

What complications result from varicella? The most common complications from varicella are bacterial infections of the skin and soft tissues in children and pneumonia in adults. Infections may be severe and include septicemia, toxic shock syndrome, necrotizing fasciitis, osteomyelitis, bacterial pneumonia and septic arthritis.
Varicella is a well described risk factor for invasive group A streptococcus infections. Other complications from varicella include cerebellar ataxia, encephalitis and hemorrhagic complications leading to bleeding disorders including disseminated intravascular coagulation.

3. Why vaccinate children for what is usually a benign disease? Why not allow children to acquire natural infection and offer vaccine only to susceptible adolescents and adults?

   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.

4. 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.

5. 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.

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

Yes. 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).

For more information, visit the following site:
http://www.cdc.gov/epo/mmwr/preview/mmwrhtml/rr4806a1.htm

2. 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.

1. 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.

For more information, visit the following site:
http://www.aap.org/family/chckpox.htm

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.