Rubella Outbreak among Office Workers -- New York City

From February 2 through May 13, 1983, 86 cases of clinical rubella* were reported among office workers employed at a major bank in lower Manhattan. All but three workers had onset of rash on or after March 28 (Figure 1). Fifteen (17.4%) of the cases were confirmed serologically.** The 86 employees ranged in age from 18 to 54 years. The source of the outbreak was not identified.

Three serologically confirmed cases occurred in pregnant women; infection occurred at 14, 18, and 28 weeks' gestation. None of these women had a history of rubella vaccination. One woman subsequently delivered a full-term infant with congenital anomalies, but the cause of the anomalies is not certain. The other two pregnancies have not yet reached term.

Of the 86 patients, 72 (83.7%) worked in one of three affected office buildings; of these, 56 (77.8%) were women (Table 1). The attack rate was significantly higher for women (2.1%) than for men (0.8%) (p 0.001). Also, the risk of infection was significantly higher for women of childbearing age, under 45 years old (2.6%), than for women 45 years old or over (0.8%) (p 0.02). However, work location was the most important risk factor (Table 2). Of 72 ill persons in Building A, 40 worked in offices on the 11th-14th floors. Employees on these floors were 3.8 times more likely to have rubella than office workers on other floors (p 0.001). Women of childbearing age who worked on the 11th-14th floors, the group with the highest attack rate, were 4.8 times more likely to have rubella than women of childbearing age who worked on other floors (p 0.001).

When rubella was first suspected, employees were advised to report all rash illnesses to the employee-health unit. In addition, susceptible women of childbearing age were urged to be vaccinated unless pregnant, and pregnant women were advised to stay home until their immune status was known. After rubella infection was serologically confirmed, the Department of Health established an immunization clinic in the office building from May 4 to May 9. Of 6,409 employees working in the complex, 2,362 (36.9%) were vaccinated. Women of childbearing age were counseled regarding the theoretical risk to the fetus from vaccination and the importance of avoiding pregnancy for 3 months after vaccination. Before vaccination, serum specimens were collected from approximately 1,000 women of childbearing age. The sera were stored for antibody testing for any woman who might become pregnant within 3 months after vaccination. Also, a surveillance system was established to identify pregnancies or adverse events following vaccination. As of May 23, one pregnancy in a susceptible woman and adverse events for six persons were reported. The adverse events included lymphadenopathy (4 persons), joint pain (3), diarrhea (1), dizziness (1), and sore throat (1). Reported by SM Friedman, MD, City Epidemiologist, S Schultz, MD, A Goodman, MD, S Millian, MD, New York City Immunization Program, New York City Dept of Health; LZ Cooper, MD, St. Luke's-Roosevelt Hospital Center, New York City; Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: The 86 cases reported in this outbreak may underestimate the actual number of office workers who were infected. The major source of case reports, the employee-health unit, did not conduct active surveillance for cases. Many ill employees may have stayed home or obtained medical assistance near their homes, and their cases may not have been reported. In addition, as many as a third of the cases may have been subclinical and, therefore, not recognized.

The reasons for the significantly higher attack rates for women of childbearing age are not entirely clear. Such an age group may have greater susceptibility because it was missed by mass vaccination programs directed at schoolchildren in the 1970s. However, it is also possible that greater opportunity for exposure was a factor. On the 11th-14th floors, the area where the outbreak was concentrated, 50.2% of employees were women of childbearing age compared with 39.8% of employees in the other areas of the bank (p 0.001).

More than a third of all employees were vaccinated during the 3H-day vaccination clinic. This high rate of response was elicited by publicity within the bank and in the public news media. The daily attendance rate nearly doubled (from 668 to 1,180) when the employees were informed that "measles" vaccine received in the 1960s was not appropriate protection against rubella. As evidence of the success of the program, no cases occurred more than one incubation period (16 days) after the program began (Figure 1).

Although numerous rubella outbreaks have been reported among adults (1-4), only one previous outbreak among office workers has been reported (5). The current outbreak again demonstrates that rubella transmission can occur wherever susceptible adults congregate, and again shows the consequences of a rubella outbreak: infection of pregnant women, disruption of the work setting, and loss of working time by staff (6).

The potential for rubella outbreaks in workplaces where young adults congregate will continue as long as approximately 10%-20% are susceptible (7). Preventing such outbreaks requires that both male and female employees be immune. Two strategies can be used. First, all employees who lack documentation of prior rubella vaccination or antibody can be screened serologically, and only the susceptibles vaccinated. Second, all employees who lack documentation of prior rubella vaccination or antibody can be vaccinated without prior screening. The choice of method depends on the cost of serologic testing, the cost of vaccine, the time available, and the ability to locate and vaccinate susceptibles who are identified by screening (8). The Immunization Practices Advisory Committee (ACIP) has stated that rubella vaccine may be administered without prior serologic screening to men and to women who are not known to be pregnant (7).

If rubella and congenital rubella syndrome (CRS) are to be prevented, at least four approaches need to be taken. First, all schoolchildren in grades K-12 should be required to have evidence of immunity to rubella. Second, extensive efforts should be made to vaccinate women of childbearing age. These efforts should include, as part of employee-health programs, vaccination of employees of institutions or workplaces where women of childbearing age congregate or are employed. Third, documentation of rubella immunity should be mandatory for students entering colleges and universities. Finally, all hospital personnel who might have contact with patients infected with rubella or with pregnant patients should be immune to rubella.

References

1. Greaves WL, Orenstein WA, Stetler HC, Preblud SR, Hinman AR, Bart KJ. Prevention of rubella transmission in medical facilities. JAMA 1982;248:861-4.

2. CDC. Rubella in universities -- Washington, California. MMWR 1982;31:394-5.

3. Blouse LE, Lathrop GD, Dupuy HJ, Ball RJ. Rubella screening and vaccination program for U.S. air force trainees: An analysis of findings. Am J Public Health 1982;72:280-3.

4. Crawford GE, Gremillion DH. Epidemic measles and rubella in air force recruits: Impact of immunization. J Infect Dis 1981;144:403-10.

5. CDC. Rubella outbreak in an office building--New Jersey. MMWR 1980;29:517-8.

6. Polk BF, White JA, DeGirolami PC, Modlin JF. An outbreak of rubella among hospital personnel. N Engl J Med 1980;303:541-5.

7. Immunization Practices Advisory Committee (ACIP). Rubella prevention. MMWR 1981;30:37-42,47.

8. Preblud SR, Gross F, Halsey NA, Hinman AR, Herrmann KL, Koplan JP. Assessment of susceptibility to measles and rubella. JAMA 1982;247:1134-7.

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