Abstract To assure efficacy, safety and security of medicines and products including those of cancer and infection prevention ones, the concepts of immunology and immunotherapy, treatments, therapeutics, research, reviews, approvals and according agency, nation and world-wide managements are highly important. Often rationally planned combinations of U.S. Food and Drug Administration (USFDA) approved medicines in preventing or treating the same or similar or multiple diseases are realized to be pharmacologically and biologically effective in mechanisms and toxicologically safe in applications. Because, multiple mechanisms are simultaneously combined in enhancing systemic immunities within the permissible limits of the doses. In this work, the immunology and immunotherapy aspects of both anti-cancer vaccines and anti-COVID-19 vaccines are taken into account to prevent current and future occurrences of cancer and infectious diseases. Though the intended mechanisms of actions are only disease specific and are primarily different between anti-cancer and anti-COVID-19 vaccines, their combinations are worthwhile in providing synergistic effects against carcinogenesis, metastasis and infections. Based on the chemical, biological and pharmacological input and output information for both kinetics and dynamics of vaccines including mRNA-1273, BNT162b2, and JNJ-78436735 to prevent covid-19 are explored in combinations with anti-cancer vaccines including Human Papillomavirus (HPV) Vaccine and Hepatitis B Vaccine (HBV). In addition to safety and efficacy, mRNA, viral-vector, protein and antigen mechanisms, pH, vaccine-vaccine interactions, independent and combined dose regimens, toxicities, solubilities, intrinsic and extrinsic covariates were taken into account for careful planning of combinations. Simultaneous dual combinations from both groups were improved to three to five levels of combinations. It was realized that these combinations qualify for pre-clinical followed by clinical-investigations further. Also, these conclusions promised us to explore additional new and approved vaccines of these indications. Citation Format: Narayana Garimella. Synergistic immunotherapy effects of anti-COVID-19 and anti-cancer vaccines in preventing tumors and infections [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2021 Oct 5-6. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(1 Suppl):Abstract nr P078.