Background
Due to a decline in Mpox cases after 2022 there is limited data on the effect of MVA BN vaccine (modified vaccinia Ankara vaccine, Bavarian Nordic) on Mpox disease severity, especially among people with HIV (PWH). During recent weeks the city of Hamburg (Germany) has faced a second wave of Mpox.
Methods
All cases diagnosed at a single medical center in Hamburg in 2022 (n=121), 2023 (n=6) and 2024 (n=42) were grouped according to vaccine history. Disease severity was assessed by the 7-item Mpox Severity Scoring System (MPOX-SSS). As a surrogate of viral load, we used the cycle threshold (Ct) values of initial MPXV PCR swabs performed at different anatomical sites during the first two weeks after symptom onset.
Results
Of 172 Mpox infections, 93 occurred in men who have sex with men (MSM) living with HIV (median CD4 504 cells/µl, 93% < 50 HIV-RNA copies/ml) and 79 occurred in MSM without HIV. Mean age was 40 yrs and 93% had a history of other sexually transmitted infections (STI) while 31% had at least one additional STI prevalent at the time of Mpox diagnosis. Hospitalization rate was 3.0% and no death occurred. Vaccinated cases had lower MPOX-SSS scores compared to unvaccinated cases (Figure 1) and less fever (37 vs 63%, p=0.003) and headaches/chills (41 vs 65%, p=0.008). There were no differences between subjects with incomplete or complete vaccine courses. Scores and symptom rates did not differ between PWH and MSM without HIV. Median Ct values were lowest in rectal (22.6) and genital swabs (24.2) and highest in oropharyngeal swabs (31.5). Neither vaccine history, HIV infection, year of diagnosis, higher MPOX-SSS scores nor co-existing STIs were significantly associated with Ct values at different anatomical sites. However, in 3 Mpox re-infections, both MPOX-SSS scores and viral load appeared to be relatively low, compared to cases with first Mpox infection.
Conclusions
Both incomplete and complete vaccine courses appear to reduce Mpox severity but not viral load in specimens. In the absence of severely immunocompromised cases, there were no differences regarding severity scores, symptoms or viral load between PWH and MSM without HIV.