Viral blips and virologic failures following mpox vaccination with MVA-BN among people with HIV

Objectives: The study aim was to evaluate whether mpox vaccination with modified vaccinia Ankara-Bavarian Nordic (MVA-BN) may be associated with viral blips or confirmed virologic failures (CVF) in people with HIV (PWH) receiving antiretroviral therapy and the associated factors.

Design: PWH who received MVA-BN, with HIV-RNA less than 50 copies/ml, and CD4 + lymphocytes at least 200 cells/μl in the 6 months prior to vaccination and at least 1 HIV-RNA determination within 3 months from vaccination.

Methods: The primary outcome was occurrence of viral blips (1 HIV-RNA ≥50 copies/ml) and CVF (1 HIV-RNA ≥1000 copies/ml or ≥2 consecutive HIV-RNA ≥50 copies/ml) following MVA-BN. Changes in CD4 + and CD4 + /CD8 + were secondary outcomes. Residual viremia was defined as detectable HIV-RNA less than 50 copies/ml. PWH already vaccinated against smallpox received single-dose MVA-BN. Mann--Whitney rank-sum test or chi-square/Fisher's test applied.

Results: Overall, 187 PWH were included: 147 received two doses of MVA-BN, 40 single-dose. Six viral blips [incidence rate = 1.59/100-person months of follow-up (PMFU), 95% confidence interval (95% CI) = 0.58-3.47], and three CVFs [incidence rate = 0.80/100-PMFU (95% CI = 0.16-2.33)] were observed. Two CVFs occurred at second dose with presence of detectable HIV-RNA following first one, with high compliance to antiretroviral therapy (ART). PWH with viral blips or CVFs had, prior to first vaccination, more frequently residual viremia [77% ( n = 7) versus 35% ( n = 62), P = 0.01]. No differences in ART ( P = 0.42) and number of MBA-BN doses ( P = 0.40) was found. In two cases of CVFs, ART was changed; all VBs resolved within 1 month.

Conclusion: Although rare, viral blips and CVFs following MVA-BN vaccination among PWH receiving ART were identified. Close monitoring of HIV-RNA during mpox vaccination should be encouraged.