Bisanzio D, Davis AE, Talbird SE, Van Effelterre T, Metz L, Mathieu VO, Brogan AJ. Individual-based modeling of Ebola outbreaks in the DRC to assess the impact of preventive vaccination strategies. Poster presented at the 8th International Conference on Infectious Disease Dynamics; November 30, 2021. Bologna, Italy.

Nonpharmaceutical interventions (NPI) and ring vaccination are currently used to reduce the spread of Ebola during outbreaks. Because these measures are typically implemented after an outbreak is declared, they are limited in their impact. Preventive vaccination may provide another option to help protect high-risk communities. To date, this strategy has not been widely implemented. A spatial-explicit individual-based model framework representing the entire Democratic Republic of the Congo population and Ebola transmission dynamics was built to evaluate the impact of preventive vaccination strategies when implemented alongside NPI and ring vaccination. The simulated preventive vaccination strategies focused on vaccination of healthcare workers (HW), frontline workers (FW), and the general population (GP) with varying levels of coverage (lower coverage: 30% of HW/FW, 5% of GP; higher coverage: 60% of HW/FW, 10% of GP) and vaccine efficacy (lower efficacy: 60%; higher efficacy: 90%). Compared with NPI + ring vaccination alone, the addition of preventive vaccination for HW reduced modeled cases, hospitalizations, and deaths by ~10% (lower levels of coverage and efficacy) and ~25% (higher levels). Adding vaccination of FW yielded greater improvements in outcomes (~14%, lower levels; ~37%, higher levels). Further including GP in the vaccination campaign yielded reductions of ~21% (lower levels) and ~52% (higher levels) compared with NPI + ring vaccination alone. In a scenario without ring vaccination, preventive vaccination reduced cases, hospitalizations, and deaths by ~28% (lower levels) and ~59% (higher levels) compared with NPI alone. In all scenarios, preventive vaccination strategies reduced Ebola transmission particularly during the initial phases of the epidemic, resulting in flatter epidemic curves with fewer cases during epidemic peaks. These results show that preventive vaccination may reduce Ebola cases and deaths, safeguard the health system by protecting healthcare workers, and provide more time to implement additional interventions once an outbreak begins.

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