Background: Recombinant (rec) poxviruses have been developed as therapeutic cancer vaccines. A multi-institutional, randomized phase II trial of poxviral vaccine, PROSTVAC-V/F, suggested an improvement in median overall survival in men with metastatic castration resistant prostate cancer. A phase III trial in this same population is accruing. Accumulating data suggest a favorable safety profile of the poxviral vaccines (vacs). Methods: We reviewed all vaccine injections (inj) from 297 patients (pts) in 9 clinical trials involving poxviral vaccines. Vacs consisted of rec vaccinia and rec fowlpox encoded with 3 human costimulatory molecules (TRICOM), and a) prostate specific antigen, or b) carcinoembryonic antigen +/-mucin-1. Vacs were administered at doses between 1.2x10⁸ to 2x10⁹ pfu, subcutaneously, in all pts. 21 pts were also vaccinated intra-tumorally. 84 pts received concurrent treatments, such as radiation, celecoxib, ipilimumab, samarium-153, or flutamide in 4 of these trials. All 9 trials involved granulocyte-macrophage colony-stimulating factor (GM-CSF), or rec fowlpox encoding GM-CSF as an immune adjuvant. We report the grade >=2 adverse events (AEs) at least possibly attributed to vaccine. Results: A total of 1,793 poxviral inj were given. 33% (593) of all inj were associated with grade >=2 vaccination emergent AEs. Of those, 25.3 % (454) were local inj site reactions; none serious. There was no contact transmission or inadvertent inoculation. One patient experienced grade 4 myocardial infarction and thrombotic thrombocytopenic purpura (TTP) reported as possibly related to vaccine. Below is the summary of AEs. Conclusions: Recombinant poxviral TRICOM vaccines appear safe and well tolerated at a broad range of doses, routes of administration and in combination with other treatments. Clinical trial information: NCT00081848, NCT00088413, NCT00060528, NCT00060528, NCT00078585, NCT00096551, NCT00113984.