Academy Adopts New Guidance on Mumps Immunization

In light of the current multistate mumps outbreak, the AAFP Board of Directors recently approved clinical recommendations that supplement the Academy's 2006 Recommended Childhood and Adolescent Immunization Schedule. The recommendations narrow the definition of immunity to mumps and effectively expand the number of persons for whom mumps immunization should be considered during an outbreak of the disease.

The new language, which was published in a Morbidity and Mortality Weekly Report Dispatch dated May 18, is consistent with recommendations generated by the CDC's Advisory Committee on Immunization Practices, or ACIP, and adopted by the CDC.

The MMWR Dispatch, "Update: Multistate Outbreak of Mumps -- United States, January 1-May 2, 2006," gives an overview of the outbreak, which had accounted for 2,597 cases reported in 11 states as of May 2. The outbreak, first detected in December 2005 on a college campus in Iowa, has primarily affected 18- to 24-year-olds (38 percent of cases).

Although the immunization status of reported mumps cases is still being investigated, CDC officials say they have preliminary data suggesting that the so-called attack rate of mumps virus has been highest in areas with the lowest immunization coverage -- that is, among groups with more members who have not completed the two-dose immunization series the CDC began recommending in 1989.

Specifically, CDC recommends that two doses of measles-mumps-rubella vaccine be administered to all children, with the first dose administered between ages 12 and 15 months and the second dose between ages 4 and 6 years. The two-dose series should be completed before entry to school or college unless a student has other evidence of immunity.

Although data are limited, the two-dose MMR series is thought to be nearly 90 percent effective in preventing mumps.

During a specially convened meeting on May 17, the ACIP redefined evidence of immunity to mumps as

Previously established criteria for immunity (i.e., birth before 1957, documentation of physician-diagnosed mumps or laboratory evidence of immunity) remain unchanged. Health care facilities should consider recommending administration of one dose of MMR vaccine to unvaccinated health care workers born before 1957 who do not have other evidence of immunity.

During an outbreak and depending on the specific epidemiology of the outbreak (e.g., the age groups and institutions involved), clinicians should consider administering a second dose of vaccine to adults and to children between ages 1 and 4 years who have received a single dose. In addition, health care facilities should "strongly consider" recommending that unvaccinated health care workers born before 1957 receive two doses -- spaced a minimum of 28 days apart -- if they have no other evidence of immunity to mumps.