1495. Mpox Vaccine Immunity in People Living with HIV (PLWH) During The 2022 Mpox Outbreak in New York City

BACKGROUND: The WHO estimated that in 2022 49% of people affected by Mpox were PLWH. Due to initial vaccine shortage in 2022, a 1/5 dose of vaccine given intradermally (ID) was FDA-authorized (8/9/22). The ID regimen had never been evaluated in PLWH. Here we describe the characteristics, and IgG responses of Mpox vaccination in PLWH and HIV-negative participants. [Figure: see text] METHODS: We are conducting a longitudinal, observational study of adults with and without HIV who received the JYNNEOS vaccine or had Mpox infection in NYC. Clinical, demographic information, and Mpox H3L-specific serum IgG titers are assessed. [Figure: see text] RESULTS: 145 participants are enrolled: 25% are PLWH (median CD4 685 cells/mm3), 14% had Mpox disease and 21% had prior smallpox vaccination. 71% with Mpox disease were PLWH. The cohort is racially/ethnically diverse, mostly men (81%) and LGBTQ+ (90%). A third of the participants were recruited from NYC DOHMH pop-up vaccination site (34%), followed by peer or professional referral (20% & 19%). Routes of vaccination were: SC-ID (49%), ID-ID (21%), SC-SC (20%), and ID-SC (10%). Redness (37%) & swelling (21%) at site of injection were common reactions. Prior smallpox vaccination was associated with higher and sustained IgG titers even after one vaccine dose. Excluding such participants, antibody titers start declining post-dose 2 (antibody half-life of 103 days). There was no difference in IgG titers at 3 months post-dose 2 between PLWH and HIV-negative for ID or any other route. Titers at 3 months post-dose 2 in PLWH correlated with CD4 counts. Longer interval between the two doses contributed to higher titers. Mpox infection yielded to significantly higher titers than vaccination post-dose 1, but no after 2 doses. [Figure: see text] [Figure: see text] [Figure: see text] CONCLUSION: Our study highlights the disproportionate burden of Mpox infection on PLWH. A diverse population representative of those most affected by 2022 Mpox was recruited. The vaccine, whether ID or SC, was well tolerated in PLWH and HIV-negative. More than two-thirds of participants with Mpox disease were PLWH. Individuals with prior smallpox vaccination maintain strong antibody levels post-dose 2, however, levels decline in individuals with no anterior prime. Our preliminary results show no negative impact of the ID dose regimen on antibody levels in PLWH. [Figure: see text] DISCLOSURES: Ellie Carmody, MD, MPH, AstraZeneca: Stocks/Bonds|Merck: Stocks/Bonds Lalitha Parameswaran, MD, MPH, Pfizer: Grant/Research Support Mark J. Mulligan, M.D., Lilly: Grant/Research Support|Meissa Vaccines, Inc.: Advisor/Consultant|Meissa Vaccines, Inc.: Board Member|Merck: Advisor/Consultant|Merck: Board Member|Pfizer: Advisor/Consultant|Pfizer: Board Member|Pfizer: Grant/Research Support|Sanofi: Grant/Research Support