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•Safety data confirmed the favorable benefit-risk profile of subcutaneous MVA-BN.•Intradermal administration is likely associated with increased syncopal events.•MVA-BN continues to have better cardiac safety than older, replicating vaccines. MVA-BN vaccine (Jynneos, Imvamune, Imvanex) was used widely in the 2022 mpox outbreak. This experience provides real-world evidence about the vaccine’s safety, particularly regarding intradermal use. Bavarian Nordic’s global safety database was searched for all adverse events following immunization (AEFIs) with MVA-BN. AEFI numbers were compared among administration routes. Selected events and administered doses were graphed over the mpox outbreak period. A total of 9585 AEFIs have been reported. The rate of myocarditis or pericarditis was <1 per 100,000 doses administered. Eighty-nine cases of syncope, fainting, or loss of consciousness were reported. This number rose after the August 2022 US emergency use authorization for intradermal administration, as did the proportion of all syncope AEFIs reported following intradermal administration (78,7 %). Real-world data from large-scale administration of MVA-BN has confirmed the vaccine’s established safety profile when administered subcutaneously. Intradermal administration is likely associated with increased syncopal event frequency.

•Lyophilized MVA was more immunogenic than the current liquid formulation of MVA.•The lower ID dose of MVA was immunologically non-inferior to the standard SC dose.•The ID route resulted in more erythema and/or induration than the SC route.•The ID route may increase the number of available doses in an emergency situation. Modified vaccinia Ankara (MVA) is being developed as a safer smallpox vaccine and is being placed in the US Strategic National Stockpile (SNS) as a liquid formulation for subcutaneous (SC) administration at a dose of 1×108 TCID50 in a volume of 0.5mL. This study compared the safety and immunogenicity of the standard formulation, dose and route with both a more stable, lyophilized formulation and with an antigen-sparing intradermal (ID) route of administration. 524 subjects were randomized to receive either a full dose of Lyophilized-SC, a full dose of Liquid-SC or 20% (2×107 TCID50 in 0.1mL) of a full dose Liquid-ID MVA on Days 0 and 28. Safety and immunogenicity were followed through 180 days post second vaccination. Among the 3 groups, the proportion of subjects with moderate/severe functional local reactions was significantly different (P=0.0013) between the Lyophilized-SC group (30.3%), the Liquid-SC group (13.8%) and Liquid-ID group (22.0%) only after first vaccination; and for moderate/severe measured erythema and/or induration after any vaccination (P=0.0001) between the Lyophilized-SC group (58.2%), the Liquid-SC group (58.1%) and the Liquid-ID group (94.8%) and the reactions lasted longer in the Liquid-ID group. In the ID Group, 36.1% of subjects had mild injection site skin discoloration lasting ≥6 months. After second vaccination Day (42–208), geometric mean of peak neutralization titers were 87.8, 49.5 and 59.5 for the Lyophilized-SC, Liquid-SC and Liquid-ID groups, respectively, and the maximum number of responders based on peak titer in each group was 142/145 (97.9%), 142/149 (95.3%) and 138/146 (94.5%), respectively. At 180 days after the second vaccination, geometric mean neutralization titers declined to 11.7, 10.2 and 10.4 with only 54.3%, 39.2% and 35.2% of subjects remaining seropositive for the Lyophilized-SC, Liquid-SC and Liquid-ID groups, respectively. Both the Lyophilized-SC and Liquid-ID groups were considered non-inferior (primary objective) to the Liquid-SC group. Transitioning to a lyophilized formulation, which has a longer shelf life, will not negatively impact immunogenicity. In a situation where insufficient vaccine is available, ID vaccination could be used, increasing the number of available doses of vaccine in the SNS 5-fold (i.e., from 20 million to 100 million doses).

In August 2022, in response to a global mpox outbreak, the World Health Organization recommended the Vaccinia vaccination for at-risk people. Case study. We describe a case of a HIV-negative bisexual man who developed a symptomatic mpox infection 13weeks after completing a two-dose course of subcutaneous third-generation modified vaccinia Ankara vaccines. The case likely acquired his mpox infection in the USA; was diagnosed in Aotearoa, New Zealand; and was followed-up in Australia, as he was actively travelling during his infection. This case highlights the importance of maintaining clinical suspicion for mpox in people who present with consistent symptoms, even if they are fully vaccinated. Also, as he travelled around Aotearoa, New Zealand, and Australia during his infection, this case highlights how public health authorities and clinicians can cooperate across jurisdictional boundaries to support cases and minimise the risk of onward transmission.

•Reintroduction of Variola major as an agent of bioterrorism remains a concern.•A compressed schedule of MVA was evaluated for use in a post event scenario.•MVA is well tolerated when given as two standard doses at Days 0 and 28 or 0 and 7.•A 2nd dose of MVA at Day 28 compared to Day 7 provided greater antibody responses.•INF-γ expression was greatest within 2 weeks after last vaccination. Reintroduction of Variola major as an agent of bioterrorism remains a concern. A shortened dosing schedule of Bavarian Nordic's (BN) IMVAMUNE® (modified vaccinia Ankara vaccine against smallpox) was compared to the currently recommended 0- and 28-day schedule for non-inferiority by evaluating the magnitude and kinetics of the immune responses. Subjects were assigned to receive IMVAMUNE or placebo administered subcutaneously on Days 0 and 7, Days 0 and 28, or Day 0. Blood was collected for antibody and cell-mediated immune assays. Subjects were followed for safety for 12 months after last vaccination. The primary endpoint of this study was the geometric mean antibody titers (GMT) at 14 days post last vaccination. Of 208 subjects enrolled, 191 received vaccine (Group: 0+7, Group: 0+28 and Group: 0) and 17 received placebo. Moderate/severe systemic reactogenicity after any vaccination were reported by 31.1%, 25.4%, and 28.6% of the subjects for Group: 0+7, Group: 0+28, and Group: 0, respectively (Chi-square test, P=0.77). Based on BN's Plaque Reduction Assay GMTs, Group: 0+7 was non-inferior to Group: 0+28 at Day 4, 180, and 365 after the second vaccination. On Day 14, Group: 0+7 and Group: 0+28 GMT were 10.8 (CI: 9.0, 12.9) and 30.2 (CI: 22.1, 41.1), respectively. Based on BN's Enzyme-linked immunosorbent assay, the proportion of subjects with positive titers for Group: 0+28 was significantly greater than that for Group: 0+7 after second vaccination at Days 4 and 180. By Day 14 after the second dose, the IFN-γ enzyme-linked immunosorbent spot (ELISPOT) responses were similar for Group: 0+28 and Group: 0+7. Overall, a standard dose of IMVAMUNE (0.5mL of 1x108TCID/mL) administered subcutaneously was safe and well tolerated. A second dose of IMVAMUNE at Day 28 compared to Day 7 provided greater antibody responses and the maximal number of responders. By Day 14 after the second dose, IFN-γ ELISPOT responses were similar for Group: 0+28 and Group: 0+7.

•A single dose of high titer MVA vaccine was compared to 1 or 2 standard doses.•High dose MVA was safe and well-tolerated.•Median time to seroconversion was similar between the two groups.•ELISA and PRNT peak titers after 1 high dose were higher than 1 standard dose.•ELISA and PRNT peak titers after 1 high dose were inferior to 2 standard doses. Reintroduction of Variola major as an agent of bioterrorism remains a concern. Time to seroconversion and plaque reduction neutralizing antibody titers (PRNT) of 1 or 2 standard doses (SD) were compared to a single high dose (HD) of modified vaccinia Ankara (MVA). Ninety subjects were randomized 1:1 to receive 1 HD or 2 SD of MVA subcutaneously on Days 0 and 28 in a placebo-controlled trial. Serum was collected for PRNT and ELISA. Subjects were followed for safety for the entire study. The HD was well-tolerated. Using Bavarian Nordic's ELISA, subjects in both groups achieved seroconversion by Study Day 15 (HD) and Day 28 (SD). Before second vaccination, the hazard rate of seroconverting for the HD group was 1.7 times the SD group with a median time for seroconversion of 14 days for both groups. The peak titer of one HD vaccine was superior to one dose of SD vaccine but inferior to the peak titer after the second dose of the SD vaccination regimen. Using Saint Louis University's PRNT, peak titers were 95.8 and 65.2 for the HD and SD groups, respectively, prior to second vaccination. Non-inferiority of the SD group was not established. The proportions of positives were 93.3% (42/45) and 82.2% (37/45) for the HD and SD groups, respectively. The peak titer after two standard doses was superior to that of the HD. HD MVA was safe and well-tolerated. While the hazard rate for seroconverting was significantly higher in the HD group before second dose, the effect was small as the median time to seroconversion was identical. When comparing PRNT, non-inferiority of one SD was not established and the peak titers were low for both groups. The HD peak response was inferior to the standard two-dose regimen response based on ELISA and PRNT.

Less than 200 years after its introduction, widespread use of vaccinia virus (VACV) as a smallpox vaccine has eradicated variola virus. Along with the remarkable success of the vaccination program, frequent and sometimes severe adverse reactions to VACV were encountered. After eradication, VACV has been reserved for select populations who might be at significant risk for orthopoxvirus infections. Events over the past decade have renewed concerns over the potential use of variola virus as a biological weapon. Accordingly, interest in VACV and attenuated derivatives has increased, both as vaccines against smallpox and as vectors for other vaccines. This article will focus on new developments in the field of orthopoxvirus immunization and will highlight recent advances in the use of vaccinia viruses as vectors for infectious diseases and malignancies.

•We studied sex differences in response to IMVAMUNE® using meta-analysis.•We analyzed study-specific estimates and patient-level data from randomized trials.•Men had consistently higher ELISA titers than women over time.•The geometric mean peak titer in men was 27% higher than women.•Sex should be considered in future testing of IMVAMUNE and other MVA-based vaccines. Previous research shows immune response to vaccination differs by sex but this has not been explored for IMVAMUNE®, a replication-deficient smallpox vaccine developed in response to the potential for bioterrorism using smallpox. We conducted a participant-level meta-analysis (N=275, 136 men, 139 women) of 3 randomized trials of IMVAMUNE conducted at 13 centers in the US through a federally-funded extramural research program. Studies were eligible for inclusion if they tested the standard dose (1×108TCID50/mL on Days 0 and 28) of liquid formulation IMVAMUNE, were completed at the time of our search, and enrolled healthy vaccinia-naïve participants. Models of the peak log2 ELISA and PRNT titers post-second vaccination were constructed for each study with sex as a covariate. Results from these models were combined into random effects meta-analyses of the sex difference in response to IMVAMUNE. We then compared this approach with fixed effects models using the combined participant level data. In each study the mean peak log2 ELISA titer was higher in men than women but no single study demonstrated a statistically significant difference. Combination of the adjusted study-specific estimates into the random effects model showed a higher mean peak log2-titer in men compared with women (absolute difference [men–women]: 0.32, 95% CI: 0.02–0.60). Fixed effects models controlling for study showed a similar result (log2 ELISA titer, men–women: 0.34, 95% CI: 0.04–0.63). This equates to a geometric mean peak titer that is approximately 27% higher in men than women (95% CI: 3–55%). Peak log2 PRNT titers were also higher (although not significantly) in men (men–women: 0.14, 95% CI: −0.30 to 0.58). Our results show statistically significant differences in response to IMVAMUNE comparing healthy, vaccinia-naïve men with women and suggest that sex should be considered in further development and deployment of IMVAMUNE and other MVA-based vaccines.

Smallpox vaccination with replication deficient vaccinia strains such as Modified Vaccinia Ankara (MVA) may induce protective immunity with improved safety and tolerability profiles compared with currently available smallpox vaccines. Ninety subjects were randomized equally to six groups in a partially blinded, randomized, controlled clinical trial. IMVAMUNE ® (MVA-BN ®, Bavarian Nordic A/S, Kvistgård, Denmark) vaccine or placebo was administered at Study Days 0 and 28 by subcutaneous or intramuscular injection and five groups were challenged with Dryvax ® at study Day 112. Vaccination with two doses of IMVAMUNE ® was safe and well tolerated compared to Dryvax ®. IMVAMUNE ® produced comparable cellular and humoral immune responses to one dose of Dryvax ® and the immunity induced appears robust 90 days post-vaccination by evidence of attenuated primary cutaneous reaction responses following Dryvax ®. IMVAMUNE ® vaccination prior to Dryvax ® reduced virus replication at the Dryvax ® site, decreased the size of the primary cutaneous lesion, and decreased the time to healing but did not completely ameliorate the immune response.

Infection of rabbits with aerosolized rabbitpox virus (RPXV) produces a disease similar to monkeypox and smallpox in humans and provides a valuable, informative model system to test medical countermeasures against orthopoxviruses. Due to the eradication of smallpox, the evaluation of the efficacy of new-generation smallpox vaccines depends on relevant well-developed animal studies for vaccine licensure. In this study, we tested the efficacy of IMVAMUNE ® [modified vaccinia Ankara-Bavarian Nordic (MVA-BN ®)] for protecting rabbits against aerosolized RPXV. Rabbits were vaccinated with either phosphate-buffered saline (PBS), Dryvax ®, a single low dose of IMVAMUNE ®, a single high dose of IMVAMUNE ®, or twice with a high dose of IMVAMUNE ®. Aerosol challenge with a lethal dose of RPXV was performed 4 weeks after the last vaccination. All PBS control animals succumbed to the disease or were euthanized because of the disease within 7 days postexposure. The rabbits vaccinated with Dryvax ®, a low dose of IMVAMUNE ®, or a single high dose of IMVAMUNE ® showed minimal to moderate clinical signs of the disease, but all survived the challenge. The only clinical sign displayed by rabbits that had been vaccinated twice with a high dose of IMVAMUNE ® was mild transient anorexia in just two out of eight rabbits. This study shows that IMVAMUNE ® can be a very effective vaccine against aerosolized RPXV.