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Rubella in Seattle-King County Washington MAX BADER, MD, MPH, AND PAUL BONIN, AB, MA

Introduction The development of rubella vaccine engendered controversy concerning its best use to prevent congenital rubella syndrome. In the United States, immunization of all children early in life was adopted in order to eliminate both susceptibility to and epidemics of rubella (especially the epidemic expected in the early 1970s). In Great Britain the policy has been to immunize girls at age 12 to avoid susceptibility during the child-bearing years while allowing endemic natural virus to circulate among males of all ages and pre-pubertal girls. Serologic testing of adult females for rubella antibody has been an accepted practice in both countries. Aside from cost and other factors, duration of immunity conferred by rubella vaccine is an especially important consideration with the U.S. approach because nearly two decades elapse between the time of immunization and most childbearing and in the meantime little natural virus circulates. Serologic data and rubella experience from Seattle-King County are presented here.

Method This study consisted of three parts: 1) review of historical data compiled by the Health Department on the incidence of rubella and congenital rubella syndrome in Seattle-King County; 2) sampling of the rubella serology specimens submitted to the Health Department laboratory to determine the proportion of women with antibody and the occurrence of congenital rubella syndrome; and 3) follow-up of a sample of women lacking rubella antibody to see whether rubella immunization occurred afterwards. Rubella has been a reportable disease in the State of From the Seattle-King County Health Department. Address reprint requests to Dr. Max Bader, Epidemiologist, Seattle-King County Health Department, 1102 Public Safety Building, Seattle, WA 98104. Mr. Bonin is Laboratory Director of the Department. This paper, submitted to the Journal April 25, 1977, was revised and accepted for publication May 31, 1977.

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Washington for over two decades and cases have been reported to the Seattle-King County Health Department by physicians, hospitals, and schools since 1921. There has been no change in reporting procedures during this time, including the period since introduction of rubella vaccine in 1970. In 1970, Peterson and Chinn surveyed community resources which would be most likely to encounter cases of congenital rubella syndrome.1 These were resurveyed in 1976 to obtain experience since 1970. All rubella serologies performed in Seattle-King County are submitted to the Seattle-King County Health Department laboratory. (70,217 specimens between 1973-1976). The specimens are submitted by private physicians, clinics, and hospitals. Virtually all of the specimens are from females of childbearing age (50-67 per cent prenatal). Serologic results of all specimens submitted during 1976 from newborns and infants were monitored for occurrence of congenital rubella syndrome. Serologic results related to females over age 8 were reviewed for the years 1973-76. Specimens from males, duplicate specimens, and those relating to disease exposure or to testing for seroconversion to rubella immunization during the previous year were excluded from that review. Information on the proportion of women with protective levels of rubella antibody by age was obtained by sampling. During each of the four years, randomly selected alphabetically stratified samples were drawn. The laboratory report forms in these samples were then classified according to test results and reason for specimen submission. The samples over-all ranged from 3 to 5 per cent of all specimens tested annually. Rubella serology specimens were initially tested using kaolin absorption for the hemagglutination-inhibition (HAI) tests. A reciprocal titer of at least 1:10 was required for a positive test result. Beginning in September 1975, in order to reduce the number of false negative test results, heparinmanganese chloride absorption was substituted for kaolin and a reciprocal titer of at least 1:8 was needed for a positive HAI test result. In 1975, a random sample was drawn of 50 adult women under age 25 who lacked rubella antibody based on HAI 1087

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tests performed in 1973. These were followed up by a survey of the patient's physicians to determine whether or not rubella immunization had subsequently occurred. Results were classified by reason for the' rubella test and, if known, the reason why immunization was not given. G G C~

Results

a) U)

Figure I shows the historical occurrence of rubella in Seattle-King County. Since 1973, rubella has almost disappeared with only 39 cases reported in 1976.1 During 1964, 1965 and 1966 King County had 8, 39, and 12 cases of congenital rubella syndrome. Even in 1968 there were 4 cases. However, no case of congenital rubella syndrome has been noted since 1970. During 1976, the Health Department reviewed rubella serology requests on 33 newborns and young infants who presented with various defects which conceivably could have been rubella-related. None were confirmed as due to rubella infection. The Seattle-King County Health Department first began providing rubella HAI tests for the community in February 1968. Only 317 tests were run that year and they were reserved for exposure problems. In 1969, 1,533 rubella HAI tests were run of which 10.3 per cent were seronegative. In 1970, the Health Department immunized 70 per cent of the elementary school children in King County during a "Rule Out Rubella" campaign. Cendehill strain rubella vaccine Was used to immunize children between the ages one year through elementary school age. Concordant with this effort, the laboratory expanded its rubella serology service. Since 1970, the Health Department has provided 14,000-20,000 rubella HAI tests each year as a laboratory service for King County physicians. During the study period King County had between 10,000 and 11,000 women at each age of the child-bearing range and 13,000-13,500 births annually. Thus, the rubella tests appear to comprise a substantial sample of this child-bearing age population.

Calendar years

FIGURE 1-Rubella Cases Per 10,000 Enrollment Seattle-King County Elementary Schools 1920-76

Table 1 shows the results of a sample of women tested expressed as the proportion of immune women by age for the years 1973-76. Noteworthy is the decreased level of immunity among the cohort of women age 19 in 1976. The proportion of women with immunity for all of the other age groups was higher and very similar among the individual ages. The level of immunity does not differ greatly from that found nationally.2 Year to year comparison is probably not valid due to change in the testing procedure and possible variation in the reagents used. The population tested was from the same universe for each of the years except for the cohorts at the youngest end of the spectrum, which were new to the universe or present initially in small numbers. Follow-up of the 1973 sample of 50 women who lacked rubella antibody revealed that 16 (32 per cent) had subsequently received vaccine. One-half of those who had not received vaccine failed to be immunized due to factors related to themselves which were beyond the control of their physicians. There was no difference in the findings between those

TABLE 1-Rubella Hemagglutination Inhibition Test Results by Age for Females in SeattleKing County, Washington 1973-76. Age

8-13 14 15 16 17 18

19/19+ 20/20+ 21-9/21 + 30+ Age Unk.

tTotals

Year, Number of Tests in Sample, and Per Cent with* Immuniry 1973 1974 1975 1976 No. Per Cent No. Per Cent No. Per Cent No. Per Cent

11 47 83 75 25 37 250

82 87 86 71 92 87 78

103 39 62 105 122 94 110

75 87 1 78 66 73 80

51 32 41 62 80 110 102 51 526

-

-

-

-

-

-

-

148 1004

528

80

635

76

86 93 81 89 86 75 89 86 85 90 84

26 23 25 41 45 56 61 69 184 57 72 669

85 87 96 95 82 86 77 88 90 86 89 87

Considered immune if antibody titer of 1: 10 or greater until September, 1975 and 1: 8 or more thereafter. $ The proportion of tests in the sample was 3% in 1973 and 1974, 5% in 1975, 4.7% in 1976. 1 088

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women having immunity checks and those being tested prenatally. One of seven women re-tested after receiving rubella vaccine failed to seroconvert. Until mid-1975, it had been Health Department policy to refer all teenagers and older females to their family physicians for rubella antibody tests, birth control services, and immunization as necessary. Since that time, the policy has been modified to permit seronegative women to receive rubella vaccine through the Health Department after signing a specific informed consent statement including an affidavit relating to birth control. However, few seronegative women have sought rubella vaccine through the Health Department.

Discussion It is too early to determine the long-range impact of current U.S. rubella immunization policy because babies immunized in the early 1970s will not reach child-bearing age until the late 1980s. Thus far, however, results are encouraging based upon experience with that policy as implemented in Seattle-King County. Few cases of rubella are being reported and few, if any, pregnant women are being exposed to those which are reported. No local cases of congenital rubella syndrome have been observed since 1970, whereas 439 cases annually were uncovered in the previous six-year period. Antibody levels among women of child-bearing age during 1976 indicate that women under age 19 have the same degree of immunity as women age 20 and over. Most of the former have received rubella vaccine whereas most of the latter developed their immunity only as a result of natural infection. It is the cohort age 19 which has the greatest susceptibility to rubella. This is not unexpected, because that cohort was young enough (age 7-8) in 1964-1965 for many of its members to have missed being infected with natural rubella virus during and subsequent to that epidemic and too old (age 13) in 1970 to be included in the mass Seattle-King County elementary school rubella immunization program.

Failure of U.S. rubella immunization policy in SeattleKing County should begin to be observed soon, if a serious problem is likely to occur. Among the first signs would be a decline in the proportion of serologic specimens from teenagers which show rubella immunity. The pre-schoolers of 1970, most of whom have had no natural rubella exposure, will reach the age of serologic testing for rubella antibody by 1980. Another indicator is the number of reported rubella cases and the degree to which pregnant women are exposed to them as determined when epidemiologic follow-up of case reports is made. Finally, monitoring of all rubella serologies performed on newborns and young infants can indicate the occurrence of congenital rubella syndrome. These may be the first signs of an unrecognized problem in areas where rubella case reporting is poor.

Summary Assessment of the results of rubella hemagglutinationinhibition tests from women of child-bearing age in SeattleKing County suggests no community susceptibility problem except among women age 19 in 1976. Within this cohort 23 per cent were susceptible, probably because these women were too young to experience a full exposure to natural rubella prior to introduction of rubella vaccine and too old to be immunized against rubella in the elementary schools in 1970. Follow-up of women under age 25 who were seronegative for rubella antibody indicated that one-third subsequently received rubella vaccine.

REFERENCES 1. Peterson, D. R. and N. Chinn. Rubella-induced congenital defects and rubella immunization. Northwest Medicine 70:169-70, March, 1971. 2. Center for Disease Control: Rubella Surveillance, July, 1973-December, 1975. Issued August 1976. p. 10.

Mumps in Seattle-King County, Washington 1920-1976 MAX BADER, MD, MPH

Introduction Mumps is a rather benign childhood disease which usually involves the salivary glands and runs its course in 3-10 days. Mumps can also cause meningoencephalitis, orchitis, Address reprint requests to Dr. Max Bader, Epidemiologist, Seattle-King County Health Department, 2305 N.W. 94th St., Seattle, WA 98117. This paper, submitted to the Journal May 23, 1977, was accepted for publication July 8, 1977.

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oophoritis, pancreatitis, mastitis, arthritis, myocarditis, and cranial nerve damage. Death is rare. 1 2 The risk of a more severe course of mumps illness increases with age, but only about 15 per cent of children and 35 per cent of adults who get mumps suffer more than mild clinical symptoms. Live mumps vaccine was licensed in the United States in December 1967.* The Jeryl Lynn strain grown by Hille*Killed mumps vaccine was licensed a decade or two earlier. 1089

Rubella in Seattle-King County Washington.

Public Health Briefs Rubella in Seattle-King County Washington MAX BADER, MD, MPH, AND PAUL BONIN, AB, MA Introduction The development of rubella...
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