Rubella Antibody Avidity Among Rubella Seropositive Women Attending a Tertiary Care Facility in Nigeria

Abstract

IntroductionRubella is a vaccine-preventable disease caused by rubella virus. It is usually mild, self-limiting and may be subclinical in more than 50% of cases (1). However, when acquired during pregnancy, particularly in the first and early second trimester can infect the placenta and foetus resulting in either spontaneous abortion; stillbirth/foetal death, neonate born with congenital rubella syndrome (CRS) or congenital rubella infection (CRI) without congenital defects (2). CRS may manifest as serious foetal anomalies affecting virtually all organs, especially the eyes, ears, heart and neurological system, making it the leading cause of preventable congenital defects (3). The highest risk of CRS is found in regions with high susceptibility (low seroprevalence) rates among women of childbearing age, as presence of high circulating maternal antibody (minimum serum rubella IgG level of 10-15 IUml -1 ) which indicates immunity to rubella and virtually excludes the possibility of rubella transmission to the foetus (1). IgG antibody avidity assay (ie, the strength of IgG binding to a multivalent antigen of the virus) is an adjunct test used to distinguish recent from past infections in individuals with IgG antibodies (4). Seroprevalence of rubella varies widely between countries, different parts of the same country and overtime within a particular region of a country (5). The seroprevalence among women of reproductive age is reported as greater than 90% in most developed countries (6). Rubella seroprevalence in African region range from 71% to 99% and varied by age group (range from 84% to 94% among women of reproductive age) (6). Rubella is endemic in Nigeria (7). Studies among women of child bearing age in Nigeria put seroprevalence at 66.6% in Imo, 77% in Lagos and 93.5% in Oyo (8-10). Although data on CRS in Africa are very limited and the true burden is largely unknown, the burden of the chronic disabilities from CRS is high as these disabilities incur high treatment costs thus increasing the public health importance of Rubella (7). It has been estimated that to prevent CRS the percentage of susceptible women of child-bearing age must not exceed 5.0% (11). A recent study in this environment however put the seroprevalence of rubella among pregnant women at 16.3% (12). Thus as part of the control measure, rubella serosusceptibility especially among women AbstractObjectives: The aim of this study was to determine the seroprevalence of rubella virus antibodies among women of reproductive age group and assess risk factors of rubella infection. Materials and Methods: A cross-sectional study was carried out among 285 women aged between 15 and 49 years. Enzyme-linked immunosorbent assay (ELISA) method was used to detect and quantify human immunoglobulin G (IgG) antibodies with avidity for rubella virus in sera of participants. Socio-demographic characteristics of the participants, along with recent and previous history of fever and rash among others were obtained using a questionnaire. Statistical analysis was carri...