Abstract
Early in the 2022 mpox outbreak, the US recommendation was to administer two doses of the JYNNEOS vaccine 4 weeks apart. However, because of limited vaccine supply, New York City (NYC) prioritized single dose vaccination. We estimated mpox cases averted by this strategy compared to strategies that prioritized 2-dose vaccination for a smaller portion of the population. We fit a network transmission model to incident mpox cases in NYC. Model output consisted of predicted cases over time when vaccine doses were administered with the "first-dose priority" strategy, compared with counterfactual simulations, where doses were administered to those eligible for a second dose ahead of those waiting for a first dose ("intermediate" strategy), or where individuals were preallocated full courses of the vaccine ("second-dose priority" strategy). We estimate that NYC's strategy averted 66% (IQR, 47%-78%) of potential mpox cases compared to no vaccination. This "first-dose priority" strategy averted 0.6% (IQR, -11% to 9.8%) more cases than the "intermediate" strategy, and 17% (IQR, 2.9%-38%) more cases than the "second-dose priority" strategy. Thus, for the 2022 mpox outbreak in NYC, preallocating vaccine doses to ensure full vaccination in a high-priority subset of the population would have increased the size of the outbreak.