Hindawi Publishing Corporation Infectious Diseases in Obstetrics and Gynecology Volume 2006, Article ID 13890, Pages 1–3 DOI 10.1155/IDOG/2006/13890 Clinical Study Does Rubella Immunity Predict Measles Immunity? A Serosurvey of Pregnant Women Colleen M. Kennedy,1 Barbara A. Burns,1 and Kevin A. Ault2 1 Department of Obstetrics and Gynecology, Roy J and Lucille A Carver College of Medicine, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, USA 2 Department of Gynecology and Obstetrics, Emory University School of Medicine, Atlanta, GA 30322, USA Received 17 January 2006; Revised 11 May 2006; Accepted 5 June 2006 Background. This study was undertaken to determine whether rubella immunity infers measles immunity in pregnant women. Methods. Stored serum samples were obtained from the Iowa State Hygienic Laboratory for evaluation of rubella and measles immunities with IgG enzyme-linked immunosorbent assay. Results. Nine hundred serum samples were obtained for testing. The average age of the women at the time of antepartum serum collection was 28 (range, 14 to 44) years. Measles and rubella immunity were 88% and 98%, respectively; there was no eﬀect of immunity status by age identiﬁed. Eighty eight percent of those with rubella immunity were also measles immune. There was no association between paired rubella and measles immunity identiﬁed, P < .0001. Discussion. Known rubella immunity did not infer measles immunity in our population. Thus, we recommend that pregnant women exposed to measles be tested and appropriately treated if they are found to be nonimmune. Copyright © 2006 Colleen M. Kennedy et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. INTRODUCTION Given a renewed public awareness following a recent measles outbreak in Iowa, several pregnant women inquired about their measles immunity [1]. While conﬁrmation of measles immunity is not routinely performed, determination of rubella immunity is a routine antenatal test in the United States. Consequently, we questioned whether a woman with known rubella immunity would be likely to have measles im- munity as well. A preliminary review of the literature conﬁrmed that measles immunity following vaccination is reported to be from 95% (1 dose) to 99% (2 doses), and rubella immu- nity is reported to be 85% to 90% among adults [2]. While both vaccines have a high immunogenicity, rubella immu- nity is shown to be somewhat lower than measles immunity. Thus, depending upon the paired association for immunity, rubella immunity could be useful as a predictor for measles immunity among women with known rubella immune sta- tus. While correlation of rubella and measles immunity has been reported, the more rigorous statistical tests to deter- mine paired association have not. METHODS Serum was obtained from the Iowa State Hygienic Labora- tory from samples collected between January of 2004 and November of 2004 among women seeking antenatal care in Iowa and submitted for routine testing (hepatitis B). The University of Iowa Internal Review Board approved the study. The sample size for the study was estimated based on the primary outcome measure, agreement between measles and rubella immunity in a population serum sample. The sam- ple size was calculated using McNemar’s test (paired data) with level of signiﬁcance 0.05, power 80%, rubella immunity 85%, and measles immunity 97%, which determined that 867 samples would be required to determine a paired asso- ciation of immunity status. Rubella immunity was determined by a commercially available rubella IgG enzyme-linked immunosorbent assay (ELISA) (BIO-QUANT, Inc., NY, USA). Likewise, measles (rubeola) immunity was determined with a commercially available measles IgG ELISA (BIO-QUANT, Inc.). Statistical analyses were conducted using the Statistical Analysis System version 9.0 (SAS, NC, USA) to describe the