Inclusion Criteria:  Histologically or cytologically documented gastroespohageal or gastric ademocarcinoma. Measurable disease as defined by RECIST 1.1 Adequate organ function Women of child-bearing potential and men with partners of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence)  Exclusion Criteria:  Currently receiving or has received another anti-cancer therapy within 4 weeks prior to first dose of vaccine study treatment. Currently receiving or has received CTLA4 or PD1/PDL1 inhibitor immunotherapy within 4 weeks prior to first dose of study treatment. Received an investigational agent within 28 days prior to the first dose of study drug. Untreated brain metastases; individuals with treated and stable metastases are eligible. Eligible subjects should have recovered from the acute effects of radiation therapy or surgery prior to study entry, have discontinued corticosteroid treatment for brain metastases for at least 4 weeks and are neurologically stable for 8 weeks (confirmed by MRI) prior to administration of experimental therapy Has known history of Human Immunodeficiency Virus (HIV). Received a diagnosis of hepatitis B or hepatitis C for which there is no clear evidence of natural immunity, immunity subsequent to vaccination, or successful eradication of the virus following antiviral therapy (individuals who are hepatitis C antibody positive may be enrolled if negative viral load confirmed). History of autoimmune disease including: inflammatory bowel disease (including ulcerative colitis and Crohn's Disease), rheumatoid arthritis, systemic progressive sclerosis (scleroderma), systemic lupus erythematosus, autoimmune vasculitis (e.g. Wegener's granulomatosis); central nervous system or motor neuropathy considered of autoimmune origin (e.g. Guillain-Barré syndrome, myasthenia gravis, multiple sclerosis). Individuals with vitiligo, Sjogren's Syndrome, interstitial cystitis, Graves' or Hashimoto's Disease, celiac disease, DM1, or hypothyroidism stable on hormone replacement will be allowed with Study Medical Monitor's approval. Has a history of (non-infectious) pneumonitis that required steroids or has current pneumonitis. History of receiving a solid organ transplant or allogeneic bone marrow transplant. Major surgical procedure within 28 days prior to the first dose of study drug. If female, pregnant or breastfeeding.