Guideline source: Centers for Disease Control and Prevention, Advisory Committee on Immunization Practices
Literature search described? No
Evidence rating system used? No
Published source: MMWR Recommendations and Reports, June 22, 2007
Varicella is a highly infectious disease caused by infection with varicella zoster virus (VZV) through the upper respiratory tract or conjunctiva. Infection generally results in lifetime immunity. The incubation period is from 10 to 21 days after exposure. Infected persons are contagious from an estimated one to two days before rash onset until all lesions are crusted (typically four to seven days after rash onset). VZV remains dormant in sensory-nerve ganglia, and later reactivation causes herpes zoster (shingles).
Varicella-attributable morbidity and mortality in the United States have declined substantially since the implementation of a universal vaccination program in 1995. Two live, attenuated varicella vaccines are available in the United States: Varivax, a single-antigen vaccine licensed in 1995 for use in healthy children 12 months and older, adolescents, and adults; and Proquad, a combination measles, mumps, rubella, and varicella (MMRV) vaccine licensed in 2005 for use in healthy children 12 months to 12 years of age.
The Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention released recommendations in June 2007 on the prevention of varicella; these recommendations revise, update, and replace ACIP's 1996 and 1999 statements. Previously, one dose of vaccine was recommended for children 12 months to 12 years of age. Key elements of the new recommendations are listed in Table 1, and ACIP criteria for evidence of immunity to varicella are listed in Table 2.
Although one-dose vaccination coverage has been high and varicella morbidity and mortality has diminished, the one-dose program did not prevent varicella outbreaks completely. Therefore, two 0.5-mL doses of varicella vaccine administered subcutaneously are recommended for children 12 months and older, adolescents, and adults without evidence of immunity.
The second dose should provide improved protection to children who do not respond adequately to the first dose, and it should lower the risk for breakthrough disease. In a follow-up from 1993 to 2003 of healthy children 12 months to 12 years of age who were given one or two doses of varicella vaccine, the annual risk for varicella after community exposure was 0.8 percent in children who received one dose and 0.2 percent in children who received two doses (number needed to treat = 167). The rate in children without immunity is estimated at about 14 percent.
Because of the risk for transmission of VZV in schools, all children entering school should receive two doses of varicella-containing vaccine or have other evidence of immunity. All states should require that students at all grade levels (including college) and those in child care centers receive varicella vaccine unless they have evidence of immunity.
CHILDREN 12 MONTHS TO 12 YEARS OF AGE
All healthy children should receive their first dose of varicella-containing vaccine at 12 to 15 months of age, and a second dose between the ages of four and six years (i.e., before entering prekindergarten, kindergarten, or first grade). The second dose may be administered earlier if the first dose was given more than three months previously. These recommended ages are harmonized with the recommendations for measles, mumps, and rubella vaccination and are intended to limit the period when children have no varicella antibody. Although the recommended minimum interval between the two doses for children 12 months to 12 years of age is three months, if the second dose was administered 28 days or more after the first dose, the second dose is considered valid and need not be repeated.
Whenever any components of the combination vaccine are indicated and the other components are not contraindicated, the use of licensed combination vaccines, such as MMRV vaccine, is preferred over separate injection of equivalent component vaccines. Single-antigen and combination MMRV vaccines may be administered simultaneously with other vaccines recommended for children 12 to 15 months of age and those four to six years of age. Simultaneous administration is particularly important if it is suspected a child will not return for subsequent vaccination.
PERSONS 13 YEARS AND OLDER
Persons 13 years and older without evidence of varicella immunity should receive two doses of single-antigen varicella vaccine administered four to eight weeks apart. However, if more than eight weeks elapse after the first dose, the second dose may be administered without restarting the schedule. Because the risk for transmission can be high among students in schools, colleges, and other educational institutions, students without evidence of immunity should routinely receive two doses of vaccine.
|Routine childhood schedules||Two doses recommended:|
|First at 12 to 15 months of age|
|Second at four to six years of age|
|Adults and adolescents 13 years and older||Two doses, four to eight weeks apart|
|Recommended for all adolescents and adults without evidence of immunity|
|Catch-up vaccination||Second dose recommended for all persons who received one dose previously|
|Persons infected with HIV||Two doses, given three months apart|
|Should be considered for HIV-infected children with age-specific CD4 T-lymphocyte percentages ≥ 15 percent|
|May be considered for adolescents and adults with CD4 T-lymphocyte counts ≥ 200 cells per μL|
|Antenatal screening||Recommended prenatal assessment and postpartum vaccination|
|Outbreak control||Recommended two-dose vaccination policy|
|Postexposure||Recommended within three to five days|
|Vaccination requirements||Recommended for children attending child care centers, students in all grade levels, and persons attending college or other postsecondary educational institutions|
Special consideration for vaccination should be given to persons without evidence of immunity who have an increased risk of transmission to persons at high risk for severe disease or who have an increased risk for exposure. These include health care professionals; household contacts of immunocompromised persons; those who live or work in environments in which transmission of VZV is likely (e.g., teachers, child care workers, residents and staff in institutional settings) or has been reported (e.g., college students, inmates and staff members of correctional institutions, military personnel); nonpregnant women of childbearing age; adolescents and adults who live in households with children; and international travelers.
A second dose is recommended for children, adolescents, and adults who previously received one dose. The recommended minimum interval between the first and second doses is three months for children 12 years or younger and four weeks for persons 13 years or older. However, the catch-up dose may be administered at any interval longer than the minimum recommended.
Physicians should use the recommended health maintenance visit at 11 to 12 years of age and other routine visits to ensure that all children without evidence of immunity have received two doses of varicella vaccine.
Prenatal Assessment and Postpartum Vaccination
Prenatal assessment of women for evidence of varicella immunity is recommended. Varicella in pregnant women is associated with a risk of VZV transmission to the child, which may cause congenital varicella syndrome, neonatal varicella, or herpes zoster during infancy or early childhood. Birth before 1980 is not considered evidence of immunity in pregnant women because of the potential severe consequences of infection.
Because the effects of the varicella vaccine on the fetus are unknown, pregnant women should not be vaccinated. Women without evidence of immunity should be vaccinated on completion or termination of pregnancy. The first dose of vaccine should be administered before discharge from the health care facility, and the second dose should be given four to eight weeks later. Women should be counseled to avoid conception for one month after each dose, but they may continue to breastfeed.
|Documentation of age-appropriate vaccination with a varicella vaccine:||In children who received their first dose at younger than 13 years with an interval between the two doses of 28 days or more, the second dose is considered valid|
|Preschool-age children (12 months and older) —one dose|
|School-age children, adolescents, and adults—two doses|
|Laboratory evidence of immunity or laboratory confirmation of disease||Commercial assays can be used to assess disease-induced immunity, but they may not always detect vaccine-induced immunity|
|Birth in the United States before 1980||Should not be considered evidence of immunity in health care professionals, pregnant women, and immunocompromised persons because of the possibilities of transmission to high-risk patients or to the fetus, or of severe disease|
|Diagnosis or verification of a history of varicella disease by a health care professional||For persons reporting with or reporting a history of atypical or mild disease, assessment by a physician or their designee is recommended; an epidemiologic link to a typical varicella case or to a laboratory-confirmed case, or evidence of laboratory confirmation performed at the time of acute disease, should also be sought; persons without such documentation should not be considered as having a valid history of disease because other diseases might mimic mild atypical varicella|
|Diagnosis or verification of a history of herpes zoster by a health care professional||—|
Health Care Professionals
Health care institutions should ensure that all health care professionals have evidence of immunity to varicella. Birth before 1980 is not considered evidence of immunity in this group because of the possibility of nosocomial transmission to high-risk patients. Health care professionals who have received two doses of vaccine and who are exposed to VZV should be monitored daily during days 10 to 21 after exposure and should be instructed to report fever, headache, or other constitutional symptoms and any atypical skin lesions immediately.
Health care institutions should establish protocols and recommendations for screening and vaccinating health care professionals and for management after exposures in the workplace. Health care professionals in whom a vaccine-related rash occurs should avoid contact with persons without evidence of immunity who are at risk for severe disease and complications until all lesions resolve (i.e., are crusted over or fade away) or until no new lesions appear within 24 hours.
Vaccination with the single-antigen vaccine should be considered in children who have HIV infection with an age-specific CD4 T-lymphocyte percentage of 15 percent or more, and may be considered in adolescents and adults with a CD4 T-lymphocyte count of 200 cells per μL or greater. Persons with impaired humoral immunity may be vaccinated. Single-antigen varicella vaccine should be used for persons with some degree of immunodeficiency.
Outbreak Control and Postexposure Prophylaxis
A two-dose varicella vaccination policy is recommended for outbreak control. In outbreaks among preschool-age children, two-dose vaccination is recommended, and children vaccinated with one dose should receive a second dose if three months have elapsed since the first. Although outbreak control efforts should be implemented as soon as an outbreak is identified, vaccination should still be offered when the outbreak is identified late.
Precautions and Adverse Events
Severe complications caused by vaccine virus strain are rare but include pneumonia, hepatitis, severe disseminated varicella infection, and secondary transmission. Serious adverse events (i.e., all events requiring medical attention) suspected to have been caused by varicella vaccines should be reported to the Vaccine Adverse Event Reporting System (VAERS). Forms and instructions are available athttps://secure.vaers.org/vaersDataEntryintro.htm or from the 24-hour VAERS information recording at 800-822-7967.