Current Trends Mumps -- United States, 1984-1985

For 1985, a provisional total of 2,886 mumps cases (1.2 cases/100,000 population) was reported in the United States; this is the lowest annual total since mumps became a nationally notifiable disease in 1968. The 1985 figure represents a decrease of 4.5% from the 1984 total of 3,021 cases and a 98.1% decline from 1968, the year after live mumps vaccine licensure, when 152,209 cases were reported to CDC (Figure 2).

Provisionally, for 1985, 28 of the 47 states where mumps is a notifiable disease reported fewer mumps cases than in 1984; mumps is not a notifiable disease in three states (New Mexico, Oklahoma, Oregon). One state (South Dakota) reported no mumps cases. By comparison, for 1984, 25 of the 47 states where mumps is a notifiable disease reported fewer cases of mumps than for 1983. Two states (Louisiana, South Dakota) reported no mumps cases for 1984. Mumps cases were reported from 23.3% of 2,994 reporting counties in 1984, compared with 24.8% of 2,927 reporting counties in 1983. Age and county data are not yet available for 1985.

However, national age-specific data are available for 2,654 (87.9%) of the mumps cases reported for 1984 (Table 1). As in the prevaccine era, persons under 15 years of age continued to have the highest incidence rate (4.4 cases/100,000 population). In contrast, the rate for persons 15 years of age or older was 0.4/100,000. As in 1982 and 1983, the school-aged population continued to both account for the majority of cases and have the highest risk for disease. Approximately three-fourths of mumps patients of known age reported in 1984 were 5-19 years of age. Children 5-9 years of age had the highest incidence rate (5.9/100,000) in 1984; children 10-14 years of age had the next highest (5.0/100,000). During 1982, the highest age-specific incidence shifted for the first time from the 5- to 9-year age group to the 10- to 14-year age group, primarily because of a large outbreak in Ohio among junior high and high school students. This pattern was not observed in 1983 and 1984. Although the reported mumps incidence remained essentially the same from 1983 to 1984 for persons 10-19 years of age, a 16%-18% decline was noted in other age groups for which vaccine is recommended. The largest decreases occurred among children under 10 years of age. For all age groups routinely receiving vaccine, there were declines between 1982 and 1984 of 14.7% to 56.1%, with the largest decreases observed in 10- to 19-year-olds.

Long-term age-specific data on mumps cases are available from three reporting areas that have continually collected such data (California, Massachusetts, New York City) from the time of vaccine licensure to the present (Table 2). In the years immediately following vaccine licensure (1967-1976), the highest reported incidence rate occurred among 5- to 9-year-olds, followed by children under 5 years of age. Together, these two groups accounted for over 70% of all reported cases. More recently (1980-1984), these two age groups accounted for 50% of reported cases due to disproportionate decreases in mumps incidence relative to persons 10 years of age or older. As a result, risk to children 10-14 years of age approximated that of children 5-9 years of age during 1980-1984. Conversely, the proportion of mumps cases occurring among 10- to 14-year-olds increased from 13.8% in 1967-1971 to 22.8% in 1980-1984. The proportion of total cases occurring among persons 15 years of age or older also changed from 5.8% to 27.4% between the earlier and recent periods. However, there was a 91.4% reduction in reported mumps incidence in this age group during 1980-1984 relative to 1967-1971. Independent of these temporal shifts in age distribution of mumps cases toward older children and adults, all age groups had a 90% or greater reduction in the risk of acquiring mumps for 1980-1984 relative to 1967-1971. Reported by Surveillance, Investigations, and Research Br, Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: Since licensure of live mumps vaccine in December 1967, more than 70 million doses have been distributed in the United States, with an accompanying 98.1% decrease in reported cases.

While a 1984-1985 nationwide survey found that 97% of school entrants and 93% of children attending licensed day-care centers were immunized against mumps (1), the school-aged population continues to be the group at highest risk for disease. Older children, such as those involved in outbreaks in Ohio in 1982 (2) and New Jersey in 1983 (3), represent unvaccinated cohorts that still exist in many areas of the country where compulsory state school-immunization requirements do not cover the entire K-12 cohort of school-aged children.

During the 1985-1986 school year, mumps immunization is required for school entry or school attendance in 32 states and the District of Columbia. However, this requirement applies to all students (K-12) in only 16 of 32 states. Currently, 18 states do not require proof of mumps immunity for school entry. Mumps incidence data from 1984 demonstrated that the incidence rate of mumps in states with no school mumps immunization law (1.9/100,000 population) was 1.7-fold higher than that in states with such a law (1.1/100,000). The effect of a school law was even more apparent in a mumps outbreak among schoolchildren in New Jersey (3). Children not covered by the state's school entry law had a fivefold higher risk for mumps than children affected by the law. This observation indicates that further declines in the reported mumps incidence rate can be expected as more children entering school are required to provide proof of mumps immunity for school attendance. It is clear that school immunization laws will be important to achieving the 1990 goal of less than 1,000 reported mumps cases annually (4).

Since live mumps vaccine was licensed, it has continued to be shown to be safe, effective, and cost-beneficial (2,3,5-9). A recent benefit-cost analysis based on national data for 1983 determined that an immunization program using single-antigen mumps vaccine would reduce costs associated with mumps by almost $340 million, with a benefit-cost ratio of 6.7 (9). This study found a benefit-cost ratio of 14.4 for an immunization program using combined measles-mumps-rubella (MMR) vaccine. The savings attributable to the use of combination rather than single-antigen vaccine totaled nearly $60 million. Because the potential for outbreaks will continue in unvaccinated cohorts, considerable medical and economic savings can be realized by including immunization with MMR vaccine as part of compliance with state school-immunization laws. Current data indicate that vaccine-induced immunity persists for at least 19 years and will likely be lifelong.

Appropriate administration of mumps vaccine to susceptible adolescents and young adults should be emphasized. In 1984, 305 (11.5%) persons of known age with mumps were 20 years of age or older. Older individuals are at higher risk for mumps complications. Although mumps is generally a self-limited disease, meningeal signs may appear in up to 15% of cases. Adult males are particularly at risk of orchitis, which occurs in up to 20% of clinical cases in postpubertal males.

Persons are considered immune to mumps if they have a dated record of vaccination with live mumps vaccine on or after the first birthday, documentation of physician-diagnosed disease, or laboratory evidence of immunity. Those lacking adequate documentation of mumps immunity should receive mumps vaccine. In addition, persons who received killed mumps vaccine (available in the United States from 1950 to 1978) might benefit from vaccination with live mumps vaccine. MMR is the vaccine of choice for persons likely to be susceptible to measles and/or rubella, as well as to mumps.

References

1. CDC. Unpublished data.

2. Kim-Farley R, Bart S, Stetler H, et al. Clinical mumps vaccine efficacy. Am J Epidemiol 1985;121:593-7.

3. CDC. Mumps outbreak--New Jersey. MMWR 1984;33:421-2, 427-30.

4. U.S. Public Health Service. Promoting health/preventing disease: objectives for the nation. Washington, D.C.: Department of Health and Human Services, 1980:21-4.

5. Koplan JP, Preblud SR. A benefit-cost analysis of mumps vaccine. Am J Dis Child 1982;136:362-4.

6. ACIP. Mumps vaccine. MMWR 1982;31:617-20, 625.

7. CDC. Mumps--United States, 1980-1983. MMWR 1983;32:545-7.

8. CDC. Mumps--United States, 1983-1984. MMWR 1984;33;533-5.

9. White CC, Koplan JP, Orenstein WA. Benefits, risks and costs of immunization for measles, mumps and rubella. Am J Public Health 1985;75:739-44.

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