Epidemiological Characteristics of Congenital Rubella Syndrome Cases During Rubella Epidemic in 2012-2014, Japan

Background: In 2012-2013, Japan experienced nationwide rubella outbreak and consequently congenital rubella syndrome (CRS) were reported. Methods: Descriptive analysis of all reported laboratory-confirmed CRS in 2012-2014 to the national surveillance system was conducted to evaluate public health impact of CRS. We used questionnaire for physicians to collect information especially focused on epidemiological and clinical characteristics of CRS patients and their mothers. Findings: Total 45 CRS cases were reported. Median gestational age was 38 weeks (range: 31-41 weeks) and median birth weight was 2,262 g (range: 650-3,290 g). Thirty cases (67%) had hearing impairment, 26 (58%) had congenital heart disease, and seven (16%) had cataract. Only three cases (7%) had all three manifestations of the classic triad. The most frequent manifestation observed beside triad was thrombocytopenia (33 cases, 73%). Eleven cases died when investigated, and case-fatality proportion was 24%. Majority of fatal cases (91%) were complicated by congenital heart disease and/or thrombocytopenia and died before six months old. None of mothers had received two doses of rubella-containing vaccine (RCV) prior to the pregnancy. Interpretation: High case-fatality proportion and multiple complications indicate absolute high public health impact of CRS. Even if infant do not present all manifestations of classic triad, physician should consider CRS if any of possible manifestation is observed during or post-recent rubella epidemic. Confirming receiving two doses of RCV or having enough antibody titer against rubella prior to the pregnancy are necessary to prevent CRS. Funding Statement: This study was supported by Japan Agency for Medical Research and Development (AMED) under Grant Number 16fk0108113j0001, 16fk0108202j0002, and 19fk0108066j0002. Declaration of Interests: The authors declare no conflicts of interest. Ethics Approval Statement: Ethics committee of the National Institute of Infectious Diseases approved this study (Registration No. 484).