A large rubella outbreak with spread from the workplace to the community

Context Childhood vaccination has reduced rubella disease to low levels in the United States, but outbreaks continue to occur. The largest outbreak in the past 5 years occurred in Nebraska in 1999. Objectives To examine risk factors for disease, susceptibility of the risk population, role of vaccine failure, and the need for new vaccination strat egies in response to the Nebraska rubella outbreak. Design, Setting, and Patients Investigation of 83 confirmed rubella cases o ccurring in Douglas County, Nebraska, between March 23 and August. 24, 1999 ; serosurvey of 413 pregnant women in the outbreak locale between October 1 998 and March 1999 (prior to outbreak) and April and November 1999 (during and after outbreak). Main Outcome Measures Case characteristics, compared with that of the gener al county population; area childhood rubella vaccination rates; and suscept ibility among pregnant women before vs during and after the outbreak. Results All 83 rubella cases were unvaccinated or had unknown vaccination s tatus and fell into 3 groups: (1) 52 (63%) were young adults (median age, 2 6 years), 83% of whom were born in Latin American countries where rubella v accination was not routine. They were either employed in meatpacking plants or were their household contacts. Attack rates in the plants were high (14 .4 per 1000 vs 0.19 per 1000 for general county population); (2) 16 (19%), including 14 children (9 of whom were aged <12 months) and 2 parents, were US-born and non-Hispanic, who acquired the disease through contacts at 2 da y care facilities (attack rate, 88.1 per 1000); and (3) 15 (18%) were young adults (median age, 22 years) whose major disease risk was residence in po pulation-dense census tracts where meatpacking-related cases resided (R-2=0 .343; P<.001); 87% of these persons were born in Latin America. Among pregn ant women, susceptibility rates were 13% before the outbreak and 11% during and after the outbreak. Six (25%) of 24 susceptible women tested were sero positive for rubella IgM. Rubella vaccination rates were 90.2% for preschoo l children and 99.8% for school-aged children. Conclusions A large rubella outbreak occurred among unvaccinated persons in a community with high immunity levels. Crowded working and living conditio ns facilitated transmission, but vaccine failure did not. Workplace vaccina tion could be considered to prevent similar outbreaks.