Public health implications of rubella antibody levels in California

Systematic Review of Measles and Rubella Serology Studies

Serological tests provide information about individual immunity from historical infection or immunization. Cross-sectional serological studies provide data about the age- and sex-specific immunity levels for individuals in the studied population, and these data can provide a point of comparison for the results of transmission models. In the context of developing an integrated model for measles and rubella transmission, we reviewed the existing measles and rubella literature to identify the results of national serological studies that provided cross-sectional estimates of population immunity at the time of data collection. We systematically searched PubMed, the Science Citation Index, and references we identified from relevant articles published in English. We extracted serological data for comparison to transmission model outputs. For rubella, serological studies of women of child-bearing age provide information about the potential risks of infants born with congenital rubella syndrome. Serological studies also document the loss of maternal antibodies, which occurs at different rates for the different viruses and according to the nature of the induced immunity (i.e., infection or vaccine). The serological evidence remains limited for some areas, with studies from developed countries representing a disproportionate part of the evidence. The collection and review of serological evidence can help program managers identify immunity gaps in the population, which may help them better understand the characteristics of individuals within their populations who may participate in transmission and manage risks.

Increasing rubella seronegativity despite a compulsory school law

To determine if lower rubella susceptibility persisted five to seven years after immunization legislation, we retrospectively reviewed the serologic status of 341 outpatients from 1985 to 1987 in an inner-city school age population. Seronegative rates increased significantly during the two-year study period from 4.2 to 24.5 percent (17 percent overall). (Beta = 6.8%, 95% CI = 3.3, 10.3). Charts were reviewed for 57 of 58 seronegative and 114 seropositive controls. Estimates were then made to the population of 341 subjects. Those with documented rubella immunization had a seronegative rate of 13 percent compared to 19 percent if the immunization status was unknown. For patients who received care in our clinic for less than two years, 32 percent were seronegative compared to 10 percent for those treated greater than or equal to 2 years (odds ratio = 0.31, 95% CI = 0.16, 0.60). Among patients immunized in 1977 or 1978, 33 percent were seronegative compared to 7 percent immunized at other times (OR = 0.21, 95% CI = 0.07, 0.63). Factors associated with increased rubella seronegativity include immunization in 1977 or 1978 and lack of continuity of care in our clinic. Much of the increase remains unexplained.

Rubella immunity in chemically dependent adolescent females

Congenital rubella syndrome continues to be a problem in this country because of the continued existence of a substantial susceptibility to rubella in young women of childbearing age. The objectives of this study were to determine the percentage of chemically dependent adolescent women in a residential treatment center at risk for rubella infection and to correlate their immune status with history of immunization. Although only one individual was reported as not having been vaccinated for rubella, 12.4% of the 129 subjects were found to be nonimmune by titer. No statistical relationship was found between self- or parent-reported immunization status and actual titer finding. Of the 16 women found to be not immune, only 56% were successfully vaccinated. Patient history appears to be of little value in establishing immunization status in this population. We recommend vaccination of young women in residential treatment centers who do not have documented histories of vaccination.

Rubella in the workplace: the need for employee immunization

From 1983 to 1985, the New York City Department of Health investigated five workplace outbreaks of rubella. Approximately 40 per cent of the 265 cases were detected among women of child-bearing age (15-44 years). Data are reviewed from the 1983 Financial District outbreak to illustrate the continued susceptibility of young adults, the missed opportunities for rubella immunization, and the danger of congenital infection. A comprehensive rubella immunization program is required to protect pregnant women and eliminate congenital rubella. As one important component of this effort, employee health physicians are urged to assess the immune status of women of child-bearing age and to vaccinate all susceptibles who are not pregnant.

Premarital rubella screening program: from identification to vaccination of susceptible women in the state of Hawaii

Premarital rubella screening programs are effective in identifying women of childbearing age who are susceptible to rubella. There is concern, however, that once identified, susceptible women may not be subsequently vaccinated. Therefore, a study was conducted to test the effectiveness of a motivational letter mailed at the time of serologic testing. Rubella-susceptible women identified by a premarital screening program were randomly divided into two groups: one group of 134 received a motivational letter and one group of 143 did not. Three months later, 52 percent of the women in the motivational group had been vaccinated, compared with only 24 percent (P less than 0.05) of the women in the control group. In this study, a motivational letter was found to lead to a significant increase in rubella vaccination rates among susceptible women. With the increasing emphasis on rubella vaccination programs for adult women, active approaches are necessary to identify and vaccinate susceptible women.

Clinical effectiveness of rubella vaccine in a college population

An outbreak of rash-like illness compatible with rubella occurred among the student population of a large university in Los Angeles between November 1, 1981 and January 31, 1982. A case-control study was conducted in order to estimate the effectiveness of rubella vaccine in preventing clinical rubella in this university population. Immunization and disease histories were obtained from parents and physicians for 39 cases and 86 controls. For those students with a clear documentation of immunization history, only one of 16 cases (6%) had evidence of prior rubella immunization, compared with 40 of 56 controls (71%). This yielded an estimated vaccine effectiveness of 97% (95% confidence limits of 82% to 100%). The level of protection observed for students immunized with rubella vaccine in our study population was high and comparable to that reported in other recent studies. This supports the notion that the current large reservoir of young adult susceptibles is primarily attributable to past failures to vaccinate school-age children, rather than vaccine failures.

A rubella outbreak among dental students: description of the outbreak and analysis of control measures

From February to April 1982, rubella was diagnosed in 17 Washington University dental students. The affected students represented 4.8% of all dental students and 21% of susceptible students. Because a high likelihood of rubella transmission was perceived, three adjacent university hospitals undertook an emergency program to ensure immunity to rubella in all personnel. The program reached 84.6% of all target personnel, but only 36% of physicians (p less than 0.001). We estimated that the program increased the level of rubella immunity from 92.2% to 98.1%, at a total cost of $140,274 of which $29,990 was in excess of ordinary expenditures. Our experience indicates that schools training health professionals face the possibility of rubella outbreaks unless they ensure rubella immunity in all students. The experience also supports the value of ongoing programs to ensure rubella immunity in hospital personnel. Without such programs, hospitals may be forced to undertake emergency programs that are likely to be disruptive and expensive and may have relatively little immediate measurable impact.

Control of a rubella outbreak in a dental school population

This study traces the development of a rubella outbreak; 16 clinical and one sub-clinical case were detected. Overall, the incidence of infection was higher for males than females. Susceptibility rates determined by the absence of primarily IgG antibodies indicated that class association, social contact, and preexisting susceptibility patterns influenced the differences in attack rates seen among the classes. In spite of a higher susceptibility caused in part by the number of foreign students enrolled, no infections occurred in the graduate student population. Concern for the spread of rubella to susceptible students and personnel within the dental school, among adjunct dental assistant and hygiene programs and others at the adjacent medical school and hospitals, led to a comprehensive immunization policy. All dental and medical personnel, regardless of clinical contact, must present proof of immunity or be immunized.