(P216) Evaluation of Public Health Contact Tracing for Mpox — Ten U.S. Jurisdictions, May 17–July 31, 2022

Objective: Contact tracing is a critical public health strategy used to interrupt transmission of infectious diseases, including mpox, by identifying exposed persons (‘contacts’) so that they can be notified and receive prevention services. Its success largely hinges on how many exposed contacts are reported and can be contacted by health department staff. We sought to examine the potential impact of contact tracing to interrupt mpox transmission among gay, bisexual, and other men who have sex with men (MSM).

Methods: The numbers of MSM with mpox who were reported, interviewed, named ≥1 contact, and named ≥1 sexual contact, and the number of named contacts (total and sexual only) were provided by 10 U.S. jurisdictions. We assessed these counts before and after access to mpox vaccine was expanded from postexposure prophylaxis for persons with known exposure to include persons at high-risk for acquisition (May 17–June 30, 2022, and July 1–31, 2022, respectively). Contact indices (the number of contacts divided by the number of interviewed MSM with mpox) were calculated for all named contacts and named sexual contacts for both periods.

Results: Overall, 1,986 mpox cases were reported among MSM in participating jurisdictions during the analytic period (240 before expanded vaccine access; 1,746 after expanded vaccine access). Similar proportions of MSM with mpox were interviewed before (95.0%, N=228) and after vaccine expansion (97.0%, N=1,693); the proportion who named ≥1 contact decreased during the two time periods (74.6% [N=179] to 38.9% [N=679]). The named contact index decreased 76%, from 3.31 before vaccine access expansion, to 0.81 after expansion. The named sexual contact index was less than one during both periods and decreased 60%, from 0.47 before vaccine access expansion to 0.19 after expansion.

Conclusions: During the period when mpox cases among MSM increased and vaccine access expanded, contact tracing became less efficient at identifying exposed contacts. Contact tracing benefited some people, but likely did not reach most exposed persons to offer prevention services, limiting its impact as the epidemic grew. Continued promotion of other public health strategies (e.g., decreasing number of sex partners, vaccination) is needed to reduce mpox transmission among MSM.