Jynneos with a virus titer of 1 x 108 TCID50/dose was administered via subcutaneous injection to 120 56–80-year-old vaccinia-experienced subjects. 

Subjects received either two injections of MVA (MM group) or one injection of Placebo and one injection of MVA (PM group) four weeks apart.

Safety was evaluated by assessment of adverse events (AE), focused physical exams, electrocardiogram recordings, and safety laboratories. Solicited AEs consisted of a set of pre-defined expected local reactions (erythema, swelling, pain, pruritus, and induration) and systemic symptoms (body temperature, headache, myalgia, nausea, and fatigue) and were recorded on a memory aid for an 8-day period following each injection.

The immunogenicity of the vaccine was evaluated in terms of humoral immune responses measured with a vaccinia-specific enzyme-linked immunosorbent assay (ELISA) and a plaque reduction neutralization test (PRNT) before and at different time points after vaccination.

Results

The results of this trial were published on June 21, 2016, by PLOS One. 

Vaccinations were well tolerated by all subjects. No serious adverse events related to Jynneos and no cases of myopericarditis were reported. The overall incidence of unsolicited AEs was similar in both groups.

Conclusions

The results suggest that a single dose of Jynneos in a 56–80 years old population was well tolerated and sufficient to rapidly boost the long-term B cell memory response induced by a prior vaccination with a traditional smallpox vaccine.