Shingles and Chickenpox (Varicella-Zoster Virus)

Description

Alternative Names

Vaccination

A live-virus vaccine (Varivax) produces persistent immunity against chickenpox. Data show that the vaccine can prevent chickenpox or reduce the severity of the illness even if it is used within three days, and possibly up to five days, after exposure to the infection.

The vaccine against chickenpox is now recommended in the US for all children between the ages of 18 months and adolescence who have not yet had chickenpox. Children are given one dose of the vaccine. Two doses one to two months apart are given to people over 13 years of age. To date, more than 75% of children have been vaccinated.

Recommendations for the Vaccine in Adults

Some experts suggest that every healthy adult without a known history of chickenpox be vaccinated. (About 90% of adults have a history of chickenpox so the numbers are likely to be low.) In any case, adults without such a history of infection should strongly consider vaccination if they are in the following groups:

• Adults who are at high risk of exposure or transmission (e.g., hospital or day care workers, parents of young children).
• People who live or work in environments in which viral transmission is likely.
• People who are in contact with people who have compromised immune systems.
• Nonpregnant women of childbearing age.
• Adolescents and adults living in households with children.
• International travelers.

As with other live-virus vaccines, the chickenpox vaccine is not recommended for the following:

• Pregnant women (including the three months prior to pregnancy). Of note, an encouraging study suggested that pregnant women who were inadvertently vaccinated did not face a higher risk for birth defects in their offspring.
• People whose immune systems are compromised by disease or drugs (such as after organ transplantation). The vaccine is being studied, however, for its safety in some of these patients, particularly children with cancer or other high-risk conditions. Experts report that it is safe in children with acute lymphoblastic leukemia (ALL), who should receive two doses. Certain children who are HIV positive may be candidates for the vaccine. An inactivated varicella vaccine may be safe and effective in patients undergoing bone marrow transplants when given before and after the operation.

At present, most patients who cannot be vaccinated but are exposed to chickenpox are given immune globulin antibodies against varicella virus. This helps prevent complications of the disease if they become infected.

Side Effects of the Varicella (Chickenpox) Vaccine

• Discomfort at the Injection Site. About 20% of vaccine recipients have pain, swelling, or redness at the injection site.
• Severe Side Effects. Only about 5% of adverse reactions are serious. Between 1995 and 2001, 759 serious adverse effects were reported. Such events included seizures, pneumonia, anaphylactic reaction, encephalitis, Stevens-Johnsons syndrome, neuropathy, herpes zoster, and blood abnormalities.
• Risk of Transmission. The vaccine may also produce a mild rash within about a month of the vaccination, which has been known to transmit chickenpox to others. Individuals who have recently been vaccinated should avoid close contact with anyone who might be susceptible to severe complications from chickenpox until the risk for a rash has passed.
• Later Infection. Months or even years after the vaccination, some people develop a mild infection termed modified varicella-like syndrome (MVLS). The condition appears to be less contagious and have fewer complications than naturally acquired chickenpox.

Vaccine Long-Term Effectiveness and Possible Need for a Booster

There is currently intense debate over the long-term protection of the vaccine. Such controversy is stimulated by the incidence of breakthrough infections after vaccination. It should be noted, however, that evidence is showing improvements in quality of life and better survival rates since the introduction of the vaccine. Any negative studies to date on long-term effectiveness simply raise the question of the need for booster or higher doses--not the elimination of the vaccine altogether.

Breakthrough Infections and Waning Protection in Vaccinated Children. Studies report that more than 15% of vaccinated children still develop chickenpox (called breakthrough infections). Reasons for this include the following:

• Waning Immunity. Studies on children in day care centers report that nearly half of children who had been previously vaccinated develop chickenpox. In one study, children vaccinated within three years had a much lower risk than those whose vaccinations had occurred later. Another study reported a higher risk for breakthrough infections in children who were immunized before 15 months.
• Oral Steroids. Children on oral steroids are also at higher risk for a breakthrough infection. (Children taking inhaled steroids, such as for asthma, do not appear to have this risk.)

It should be noted that if vaccinated children develop chickenpox, the cases are nearly always mild and usually less contagious. In such children, the infection appears to be caused by a wild virus, not a reactivation of the vaccine.

This does not necessarily mean, however, that children who are vaccinated eventually lose total immunity. A breakthrough infection is often due to issues with the primary vaccine (improper storage, low potency) or the child's history (having asthma, being less than 14 months at the time of vaccination). Nevertheless, there is also some evidence that either having the vaccination or even having chickenpox itself is not as protective against a later infection as experts have thought.

Long-Term Protection in Vaccinated Adults. The protective effect for adults is even less clear. An encouraging 2002 study of adults vaccinated between 1979 and 1999 reported that although 9% developed chickenpox months to years after their last vaccination, in all cases, infection was mild, with none of the serious complications of adult chickenpox. A 2003 study on booster shots in older adults suggests that revaccination with the live virus is safe and effective.

Vaccine's Effect on Shingles. A primary concern is whether the vaccine protects against shingles later on, particularly in people who have breakthrough infections--however mild. As more and more children get vaccinated, the actual protection of the vaccine and the implication of the breakthrough infection will become clearer.[For more information,seeWell-Connected Report #90,Immunizations.]

Varicella-Zoster Immune Globulin

Varicella-zoster immune globulin (VZIG) is a substance that triggers an immune response against the varicella-zoster virus. It is used to protect high-risk patients who are exposed to chickenpox, or those who cannot receive a vaccination of the live virus. Such groups include:

• Pregnant women with no history of chickenpox.
• Newborns under four weeks who are exposed to chickenpox or shingles.
• Premature infants.
• Immunocompromised children and adults with no antibodies to VZV.
• Recipients of bone-marrow transplants (even if they have had chickenpox).
• Patients with a debilitating disease even if they have had chickenpox.

VZIG should be given within 96 hours and no later than 10 days after exposure to someone with chickenpox.