Modelling the impact of vaccination and sexual behavior change on reported cases of mpox in Washington D.C.

BackgroundThe 2022 mpox outbreak infected over 30,000 people in the United States. Infections were commonly associated with sexual contact between men. Interventions included vaccination and reductions in sexual partnerships. We estimated the averted infections attributable to each intervention using mathematical modeling. MethodsWe fit a dynamic network transmission model to mpox cases reported by the District of Columbia through January 2023. We incorporated vaccine administration data and reported reductions in sexual partnerships among gay, bisexual, or other men who have sex with men (MSM). Model output consisted of predicted cases over time with or without vaccination and/or behavior change. ResultsWe estimated initial case reductions were due to behavior change. Vaccination alone averted 64% [IQR:57%-72%] and behavior change alone averted 21% [IQR:11%-29%] of cases. Vaccination and behavior change together averted 80% [IQR:74%-85%] of cases. In the absence of vaccination, behavior change reduced cumulative cases but also prolonged the outbreak. ConclusionsInitial case declines were likely caused by behavior change, but vaccination averted more cases overall. Overall, this indicates that encouraging individuals to protect themselves was vital in the early outbreak, but that combination with a robust vaccination program was ultimately required for control.