Diverse sensors and smart devices are promising in facilitating to perform specific tasks which generate massive data whilst such data transmission is challenged in the big data era. Under some circumstances, these devices may form Mobile Opportunistic Networks (MONs) which are characterized by intermittent connectivity. In such scenarios, there is a critical issue that nodes with the already delivered message copies may continue carrying and transmitting the copies if they are not informed that the message has been delivered. This may result in redundant data, and thus large consumption of network resources and network performance degradation. To avoid generating, transmitting and storing unwanted data due to redundant message copies, we propose an Immunization-Based Redundancy Elimination scheme (IBRE) in MONs to stop useless data transmission and flush redundancy. In IBRE, each destination independently selects the right number of ACKs distributed to respond to the variation of the amount of redundant data in a dynamic fashion. Simulation results demonstrate that IBRE suppresses redundant data transmission and eliminates useless data generated from redundant message copies in cost-efficient manner.