Current Trends Rubella and Congenital Rubella -- United States, 1980-1983

RUBELLA

Although the incidence of reported rubella has fluctuated slightly over the past several years, a downward trend has been observed for most of the United States. A review of data for the period January 1, 1980, through September 24, 1983, indicates that if no sudden change in reporting patterns occurs, the final rubella incidence rate for 1983 should be at an all-time low.

In 1980, a total of 3,904 cases of rubella were reported to CDC; this represents an incidence of 1.7 cases per 100,000 population (Table 1). The 1981 incidence (0.9/100,000) was the lowest reported since rubella became a notifiable disease in 1966 (Figure 1); 2,077 cases were reported in 1981, a decline of 47% from the 1980 total. In 1982, 2,325 cases of rubella were reported in the United States (incidence 1.0/100,000)--a 12% increase over the 1981 total. The increased occurrence in 1982 reflected an increase in cases of rubella in California, primarily among adolescent and young-adult populations and particularly in hospitals and universities. California, which reported almost three times as many cases in 1982 (1,437 cases) as in 1981 (533), accounted for 62% of all cases nationwide. In the rest of the nation, the number of reported rubella cases was 42% lower in 1982 than in 1981. In 1980, only one state reported no cases of rubella. Five states and the District of Columbia reported no cases in 1981, and seven states reported none in 1982. The number of counties reporting rubella declined from 676 (21.5% of all counties) in 1980, to 494 (15.7%) in 1981, to 366 (11.7%) in 1982.

During the first 38 weeks of 1983 (ending September 24, 1983), 791 cases were reported, a 61% decrease from the number reported during the same period in 1982. Fifteen states and the District of Columbia have reported no cases thus far in 1983, twice as many reporting areas as were free of rubella during the same period in 1982. Sixty percent of cases reported thus far in 1983 are from four reporting areas (California, Florida, New York City, Texas). Although the California cases alone currently account for 28% of the 1983 cases, rubella activity in California is down by 83% compared with 1982 figures from the same period.

The age-specific incidence rate of rubella in children under 15 years of age decreased over the past 3 years. While children under 5 years of age still had the highest overall incidence rate in 1982 (2.7 reported rubella cases per 100,000 population), they accounted for a lower proportion of all cases in 1982 (20%) than in 1981 (37%). In contrast, the incidence rate for those 15 years of age and older, noted to have been lower in 1981 (0.4/100,000) than in 1980 (1.0/100,000), increased somewhat in 1982 (0.8/100,000). Persons 15 years of age and older accounted for a much higher proportion of cases in 1982 (62%) than in 1981 (37%). Although between 1981 and 1982 the incidence rates increased for all age groups 15 years of age and older, the greatest increase occurred in the 25- to 29-year age group, which experienced almost a threefold increase in disease (Table 1). The increase in reported incidence rates for adolescents and young adults in 1982 over those reported in 1981 again reflects rubella activity in California; this state accounted for 74% of all 1982 cases in persons 15 years of age and older. If California cases are excluded, the incidence rates for persons 15 years of age and older decreased by 17% between 1981 and 1982. When rates for 1980 and 1982 are compared, age-specific incidence rates in 1982 were higher only for persons 25 years of age and older (a 50% increase); 1982 rates were lower for 15- to 24-year-olds. CONGENITAL RUBELLA SYNDROME

Detailed reports of cases of congenital rubella syndrome (CRS), including clinical signs and laboratory results, are voluntarily submitted by local and state health departments to two different morbidity systems: the National Morbidity Reporting System (the reporting system for the MMWR) and the National Congenital Rubella Syndrome Registry (NCRSR), maintained at the Division of Immunization at CDC. Cases reported to the MMWR are reported without clinical and epidemiologic data and are counted by year of report. In contrast, cases reported to the NCRSR are classified according to specific criteria and are reported by year of birth.* Data for a given year are reported as provisional until at least 3 years have elapsed. According to the NCRSR, the incidence rates of confirmed and compatible CRS have declined substantially since 1979 (Figure 2). Fifty-five cases were reported in 1979, 14 were reported in 1980, and nine were reported in both 1981 and 1982. California reported seven of the nine cases in 1982 and is the only state that has reported cases in 1983 (three cases, all with estimated dates of conception in 1982). Almost all CRS cases continue to be reported within the first year of birth (1). Reported by Surveillance and Investigations Section, Surveillance, Investigations, and Research Br, Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: The goal of rubella vaccination programs is to prevent congenital rubella infection.** The vaccination strategy adopted by the United States in 1969, the year rubella vaccine was licensed, was aimed at controlling rubella in preschool and young school-aged children, the known reservoirs for rubella transmission. The intention was to thereby prevent exposure of susceptible, pregnant females to rubella virus (2). Accordingly, the primary target group for vaccine was children of both sexes. Secondary emphasis was placed on vaccinating susceptible adolescents and young adults, especially women. By 1977, vaccination of children 12 months of age and older had resulted in marked declines in reported rubella incidence in children and had interrupted the characteristic 6- to 9-year rubella epidemic cycle; however, this vaccination strategy had less effect on rubella incidence in persons 15 and over (i.e., childbearing age for women) (Table 2). Approximately 10%-20% of this latter population continued to be susceptible (3-5), a proportion similar to that of prevaccine years (6). Most importantly, reported endemic CRS continued at a low but constant level (7). When this problem was recognized, public health authorities targeted other groups for vaccination. Increased efforts were made to vaccinate junior and senior high school students and enforce rubella immunization requirements for school entry (8). Also, all susceptible military recruits began to receive rubella vaccine (9).

Published accounts of rubella outbreaks in hospitals have caused concern about the need to screen and/or vaccinate susceptible personnel (10,11). A number of states have considered requiring proof of rubella immunity for college entrance (12). These factors, combined with the 1977 Childhood Immunization Initiative and the 1978 Measles Elimination Initiative (which encouraged use of combined measles and rubella vaccine), have led to decreases in reported rubella cases in all age groups.

The number of doses of rubella vaccine administered in the public sector to persons 15 years of age and older doubled between 1978 and 1981. By 1981, incidence rates for adolescents and young adults were lower than those for young children (Tables 1 and 2). Compared with rates for prevaccine years, by 1981 the overall reported incidence of rubella had declined by 96%, with a 90% or larger decrease in cases in all age groups. Predictably, the number of reported CRS cases started to decline further (Figure 2).

Although the increase in reported rubella incidence in older individuals in 1982 was not reported nationwide, outbreaks in this population can still occur. Until the susceptibility rate of postpubertal women is effectively lowered, CRS will continue to occur, each case at an estimated lifetime expenditure of $221,600 (13). While CRS will eventually be eliminated as currently young, vaccinated cohorts enter the childbearing years, the process is slow and costly in human life and health resources. Only nine CRS cases were reported in 1982; however, this figure represents only an estimated one-tenth of the total case count (14). The only effective means to rapidly eliminate CRS is to intensify efforts to vaccinate susceptible, postpubertal individuals.

Immunizing this population, especially women of childbearing age, will require a multifaceted approach (15). Some recommended activities include: (1) making the general public and health-care providers more aware of the dangers of rubella infection; (2) ensuring that patients are vaccinated as part of routine medical and gynecologic care; (3) ensuring vaccination of all women visiting family planning clinics; (4) ensuring vaccination of unimmunized women immediately after they undergo childbirth, miscarriage, or abortion; (5) vaccinating susceptible women identified by premarital serology; (6) vaccinating hospitalized women before discharge; (7) requiring proof of immunity (a positive serologic test or documented rubella vaccination) for college entry; and (8) requiring proof of immunity for all hospital personnel who might be exposed to patients with rubella or who might have contact with pregnant patients. These

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