Rubella vaccination of unknowingly pregnant women during mass campaigns for rubella and congenital rubella syndrome elimination, the Americas 2001-2008.

Background: Due to the significant teratogenicity of rubella virus and the use of a live-attentuated vaccine, pregnancy is a contraindication of receipt of rubella vaccine (RCV). Data collected from several countries that have observed susceptible women who had received RCV during pregnancy documented that no infant with congenital rubella syndrome (CRS) has been born, so the risk is theoretical. As part of the regional initiative to eliminate rubella and CRS in the Americas, one of the key strategies was the vaccination of women of childbearing age. The implementation of mass vaccination campaigns targeting women of childbearing age in Argentina, Brazil, Costa Rica, Ecuador, El Salvador, and Paraguay provided an opportunity to further increase the body of knowledge on the safety of rubella vaccine if an unknowingly pregnant woman is vaccinated in early pregnancy.

Methods: Using a standard protocol, women who were unknowingly pregnant or become pregnant ≤ 30 days after receiving RCV were evaluated to determine immunity status (eg, susceptible, immune, and unknown) at the time of vaccination. Susceptible pregnant women were observed to determine the outcome of the pregnancy. For pregnancies that resulted in live births, serum samples were obtained from the newborn for rubella immunoglobulin (Ig) M antibody testing. If the newborn's serum sample was IgM positive, the infant was evaluated for manifestations of CRS.

Results: During the period 2001-2008, 48748253 women of childbearing age were vaccinated in the region of the Americas, 39542253 (81%) of whom were vaccinated in the 6 selected countries. Of these women, 30139 (0.07%) were pregnant or became pregnant ≤1 month after receiving vaccine and were followed up. On the basis of serological evaluation, 2894 (10%) women were classified as susceptible at the time of vaccination; of their pregnancies, 1980 (90%) resulted in a live birth. Sera from 70 (3.5%) of these infants were rubella IgM antibody positive, but none of the infants had features of CRS as a result of rubella vaccination. The maximum theoretical risk for CRS following rubella vaccination of susceptible pregnant women was 0.2%. Conclusions. The results of these studies from 6 select countries provides additional evidence showing an absence of risk of CRS associated with administering rubella vaccine shortly before or during pregnancy.