The only effective method of preventing rubella virus infection is by vaccinating women who lack the antibodies IgG-RUB, which have been proven to prevent rubella. In these study we analyze the natural seroconversion against rubella virus among women in the procreative ages of 23-30 with ELFA assay (enzymimmunofluorescence assay), using a mini-VIDAS instrument. 7.8% of 148 women tested lacked IgG-RUB. Such seronegative women should be vaccinated before pregnancy.