CHICAGO - The American Academy of Pediatrics (AAP) recently updated its recommendations for use of varicella vaccine (Varivax, Merck) and is calling for universal immunization of healthy children older than 12 months and pediatrician-supported immunization requirements for child care and school entry.
The policy is the first update since the original was released in 1995 and tackles immunization barriers, highlights use of the vaccine in children with HIV, examines postexposure immunization and provides guidelines for storage and administration.
Despite the effectiveness of varicella vaccine, many U.S. children remain unvaccinated resulting in continued illness, hospitalization and even death. From July 1997 to June 1998, varicella vaccine coverage for children ages 19 to 35 months was estimated at only 34%, with variations ranging from 6% to 52% depending on state and urban areas.
Before the availability of the vaccine in 1995, approximately 4 million cases of chickenpox were reported each year in the United States - resulting in 10,000 hospitalizations and 100 deaths. Ninety percent of infections, two-thirds of chickenpox-related hospitalizations and nearly half of chickenpox-related deaths occurred in children.
Varicella vaccine is 85% effective in preventing all cases of chickenpox and almost 100% effective in preventing severe cases. It is also effective if administered within three days postexposure. Adverse events occur with an overall frequency of 5% to 35%. Approximately 20% of those immunized will have minor injection-site reactions like pain, redness or swelling; 3% to 5% will develop a local rash; and another 3% to 5% will develop a varicella-like rash. Serious adverse reactions are rare in association with the vaccine. The vaccine has also been deemed cost beneficial when direct medical and indirect societal costs were considered, according to the AAP.
The revised statement also tackled barriers blocking high rates of immunization, including the misconception that varicella is a mild disease; concerns about vaccine safety and effectiveness; concerns about waning immunity; concern that universal immunization of young children will shift disease burden to an older population; stringent storage and handling requirements for the vaccine; availability; inadequate insurance coverage; and lack of vaccine requirements for licensed child care and school entry.
The Advisory Committee on Immunization Practices recently revised its guidelines for school and day care entry. It recommended a physician's diagnosis of varicella, a reliable history of the disease, serologic evidence of immunity or receipt of the varicella vaccine be required for enrollment in child care centers and schools. The Department of Health and Human Services, in its recently released Healthy People 2010 also listed objectives for varicella vaccine coverage of more than 90% for children ages 19 to 35 months and more than 95% at school entry. Many states are also considering mandating varicella immunization before entry into child care centers or school.
The AAP now recommends that children 12 months or older, who have not received varicella vaccine, should receive a dose immediately. They also recommend immunization of susceptible older children and adults because the level of severe complications increases with age. The vaccine may also be effective for preventing or modifying the disease if given postexposure within three days of the appearance of the rash.
According to the AAP, children with chickenpox are also more likely to contract severe, invasive, group A streptococcal disease. Adults who contract the disease, though fewer in number than children, have a ten- to 20-fold higher risk of complications and death.
Varicella vaccine, however, should not be routinely administered to children with cellular immunodeficiencies such as leukemia, lymphoma, malignancies affecting bone marrow or lymphatic systems or congenital T-cell abnormalities. Children infected with HIV may be at increased risk of morbidity from varicella and herpes zoster; however, data shows the vaccine is safe, immunogenic and effective for children with HIV.
Because Varivax is temperature sensitive, the vaccine should be stored in a freezer with an average temperature of -15° C (5° F) or colder. New data indicate, however, it is safe and acceptable to store the vaccine at refrigerated temperatures of 2° C to 8° C (36° F to 46° F) for up to 72 hours before use. The vaccine must be used within 30 minutes once reconstituted or discarded if not used within that time.
Follow-up studies of children immunized in clinical trials indicated that immunity protection continued for at least 11 years following the vaccine. Additional studies in Japan have suggested that immunity may last for at least 20 years. Data from other live virus vaccines, such as measles and rubella, suggest immunity remains high throughout life. Studies are currently underway to determine the need, if any, for additional doses of varicella vaccine.
Despite the effectiveness of varicella vaccine, many U.S. children remain unvaccinated resulting in continued illness, hospitalization and even death.
Varicella vaccine is 85% effective in preventing all cases of chickenpox and almost 100% effective in preventing severe cases.
It is effective if administered within three days postexposure.
Side effects occur with an overall frequency of 5% to 35%. Approximately 20% of those immunized will have minor injection-site reactions like pain, redness or swelling; 3% to 5% will develop a local rash; and another 3% to 5% will develop a varicella-like rash. Serious adverse reactions are rare in association with the vaccine.
For more information:
- AAP Committee on Infectious Diseases. Varicella vaccine update. Pediatrics. 2000;105(1):136-141.
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