Burden of congenital rubella syndrome after a community-wide rubella outbreak, Rio Branco, Acre, Brazil, 2000 to 2001

Abstract

Background. During 1999 and 2000 rubella outbreaks were reported in 20 of 27 states in Brazil, many among young adults. We investigated a large rubella outbreak in Rio Branco, Acre, in northwestern Brazil, where rubella vaccination targeting children 1 to 11 years old had been introduced in April 2000. Surveillance for congenital rubella syndrome (CRS) was initiated after the outbreak. Methods. Suspected rubella cases were detected through active and passive surveillance. Confirmed rubella cases were patients with fever, rash and rubella-specific IgM antibodies. Suspected CRS cases were infants born with CRS-compatible defects or born to mothers with a history of rubella during pregnancy. Confirmed cases were infants with CRS-compatible defects and rubella-specific IgM antibodies. Results. From April 1 to December 31, 2000, 391 confirmed rubella cases were reported. The incidence among persons ages 12 to 19 years (3.3 per 1000 population) was increased 3.7-fold relative to children ages 1 to 4 years (95% confidence interval, 2.4 to 5.8). Of 21 infants with suspected CRS cases, 17 (91%) were tested for rubella-specific antibodies, of whom 7 were IgM-positive and 5 had confirmed CRS. The peak incidence of confirmed CRS (4.3 per 1000) was in March 2001, 7 months after the outbreak peak, with an annualized incidence of 0.6 per 1000. Conclusions. Vaccination among school age children was insufficient to prevent a rubella outbreak among young adults that resulted in the occurrence of at least 5 cases of CRS. To prevent further cases of CRS, outbreak vaccination of young adults was conducted in November 2000 and among women ages 12 to 39 years in 2001 as part of a national campaign, with a coverage of 98% statewide.