Follow-up Study of Unknowingly Pregnant Women Vaccinated Against Rubella in Brazil, 2001-2002 EDITORIAL COMMENT

Abstract

Rubella infection during pregnancy is associated with a range of fetal malformations referred to as congenital rubella syndrome (CRS). An efficacious, safe, and affordable vaccine with a highly favorable cost-benefit ratio of vaccination is available. Following reports between 1997 and 2001 from several Brazilian states with increased incidence of rubella among women of childbearing age and infants born with suspected CRS cases, there was a nationwide mass immunization of women of childbearing age with the vaccine in 2001 and 2002. Because of concerns that some women were unknowingly pregnant at the time of mass immunization, follow-up surveillance was conducted to detect potential adverse effects on the fetus among women vaccinated during pregnancy or just before conception. This follow-up study evaluated the safety of the vaccine in infants of susceptible pregnant women inadvertently vaccinated during pregnancy or before conception who were identified with the surveillance system. To determine susceptibility to rubella infection, serologic tests for anti-rubella immunoglobulin (Ig) M and IgG-specific antibodies were performed. Susceptible women were followed until delivery. The presence of congenital rubella infection in live-born infants born to vaccinated women was defined as a positive anti-rubella IgM test. Infected infants were tested for viral shedding and observed for 12 months for signs of CRS. Data on the incidence of congenital rubella infection were obtained from 7 of the 27 states in Brazil that conducted active follow-up. Of the 22,708 cases of rubella vaccination in pregnant women reported nationwide, 20,536 (90%) occurred in the 7 states. Among the cases, 11.4% (2332/20,508) of women were susceptible to rubella at the time of vaccination. Serologic testing showed that 4.1% (67/1647) of the newborns had rubella IgM antibody indicating congenital infection (95% confidence interval, 3.2-5.1). No cases of CRS were found in infected infants born to vaccinated mothers. These findings show that the use of the rubella vaccine to immunize susceptible women of childbearing age is a safe and effective strategy for prevention of rubella infection and CRS.