Seroepidemilogical Study & Vaccine Efficacy of Rubella in Girls at Marriage: Kermanshah, Iran, 2006

Rubella is a mild viral infectious disease usually occurs sub-clinically without a serious complication, but if occur during pregnancy, specially the first trimester, its etiologic agent can transmit and invade to fetus causing congenital rubella syndrome (CRS) or fetal death. In order to prevent disease and its congenital complications, Rubella immunization is currently done in many countries. Nearly 20 % of girls at marriage were susceptible to rubella in 2003. That is why early all Iranians at the age of 5-25 years old were vaccinated against rubella and the vaccine was included in the compulsary immunization, MMR afterwards. This cross-sectional and analitical study was carried out on 140 girls who attended at a marriage consultancy center in Kermanshah city. Annually, about 10000 girls attend Rafattieh Health Center for pre-marriage laboratory tests in Kermanshah. It was expected that rate of sero-positive Rubella increase from 80 % in 1999 to above 90 % at the study time after mass and national vaccination. So considering 95 % of confidence. All Samples were tested using ELISA serologic method. Antibody positivity and immunity against rubella was seen in 99.3 % (139 out of 140 vaccinated girls), while it was 80 % according to the similar study conducted on 240 unvaccinated girls at the same place in 1999. Comparing these two studies showed that attack rate (sero-negativity) has been decreased from 17.08 % in unvaccinated to 0.71 % in vaccinated ones with a confidence interval of 0.01- 0.30 (p < 0.01). The vaccine efficacy is estimated 96 %. Relationship between immunity, age, education and history of rubella-like illness, could not be assessed because only 1 (< 0.1%) of 140 vaccinated girls was not immune. In our previous studey in 1999 we had recommended to screen for susceptibility to rubella before marriage, which is no longer required since more than 99 % of vaccinated girls showed immuninty at the time of marriage. However, as sustainability of immunity after rubella vaccination is usually less than immunity due to illness, we recommend screening for rubella protective antibody every few years.