All health care workers should receive two doses of the measles-mumps-rubella vaccine if they do not have evidence of immunity, the Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention voted during a special meeting that was held by telephone in response to the multistate outbreak of mumps that began in Iowa late last year.
Between Jan. 1 and May 2, 11 states reported 2,597 cases of mumps. Eight states (Illinois, Iowa, Kansas, Missouri, Nebraska, Pennsylvania, South Dakota, and Wisconsin) reported mumps outbreaks (five or more outbreak-associated cases) with ongoing local transmission or clusters of cases. Three states (Colorado, Minnesota, and Mississippi) reported cases associated with travel from an outbreak state.
The majority of mumps cases (1,487, composing 57%) were reported from Iowa; states with the next highest case totals were Kansas (371), Illinois (224), Nebraska (201), and Wisconsin (176). Of the 2,597 cases reported overall, 1,275 (49%) were classified as confirmed, 915 (35%) as probable, and 287 (11%) as suspect. For 120 (5%) cases, classification was unknown (MMWR 2006:55[Dispatch];1–5).
To prevent mumps, ACIP has long recommended a two-dose MMR vaccination series for all children, with the first dose administered at ages 12–15 months and the second dose at age 4–6 years. Two doses of MMR vaccine are recommended for school and college entry unless the student has other evidence of immunity.
In the specially convened meeting—the results of which are considered interim—the committee redefined evidence of immunity to mumps through vaccination as follows: One dose of a live mumps virus vaccine for preschool children and adults not at high risk; two doses for children in grades kindergarten through 12 and adults at high risk (such as persons who work in health care facilities, international travelers, and students at post-high school educational institutions). Other criteria for evidence of immunity remain unchanged.
Furthermore, health care facilities should consider recommending one dose of MMR vaccine to unvaccinated health care workers born before 1957 who do not have other evidence of mumps immunity.
During an outbreak and depending on the epidemiology of the outbreak (the age groups and/or institutions involved), a second dose of vaccine should be considered for adults and for children aged 1–4 years who have received one dose. The second dose should be administered as early as 28 days after the first dose. In addition, during an outbreak, health care facilities should strongly consider recommending two doses of MMR vaccine to unvaccinated workers born before 1957 who do not have other evidence of mumps immunity.