Zika virus seroprevalence in women who gave birth during Zika virus outbreak in Brazil - a prospective observational study

Background: The recent Zika virus (ZIKV) outbreak in Brazil started in August 2015 and ended in May 2017 without effective public health measures for its control have been taken. The immunological status of a community may not only predict future outbreaks as well to answer questions regarding ZIKV not known yet. Objective: To verify the seroprevalence of ZIKV in a group of women who were pregnant during the Zika virus outbreak in Recife, three to nine months after the delivery, and to evaluate the neurodevelopment of their children. Methods: A cross-sectional study enrolled participants of a cohort study held at Instituto de Medicina Integral Professor Fernando Figueira (IMIP) during the ZIKV outbreak in Recife. Mothers who gave birth between the last trimester of 2015 and the first semester of 2016, period of the peak of microcephaly outbreak in Recife, were invited. All participants had the serum tested by the anti-ZIKV IgG/IgM enzyme-liked immunosorbent assays, ELISA kit (Euroimmun, Lubeck, Germany). All children whose mothers presented positive serology for ZIKV performed the IgG/IgM ELISA test for ZIKV. These children were also evaluated by a neuropediatrician and the Denver II development screening test was applied. Results: Among the 132 studied pregnant women who gave birth at the peak of ZIKV outbreak in Recife, all were ZIKV IgM negative and 81 (61,3%) had ZIKV IgG positive. Mothers ZIKV IgG positive had more fever and rash during the pregnancy as compared with mothers negative for ZIKV; respectively 27/81 (33,3%) vs 6/51 (11,7%), p = 0.005 and 22/81 (27,2%) vs 4 (7,8%), p = 0.016. Only one child had IgG positive serology for ZIKV. No children had neurodevelopment defect for the age group and the Denver II normal scores. Conclusions: A high ZIKV IgG seroprevalence in pregnant women at the end of the ZIKV outbreak in Recife was found. This finding suggests that community protective immunity may have contributed to the end of ZIKV outbreak in Recife, Brazil.