The most promising method of containing the COVID-19 pandemic is considered to be vaccination against SARSCoV-2 infection. However, research on the relationship between vaccination against COVID-19 and cancer has primarily examined induced immunity rather than the disease itself. Considering that breast cancer is the most common cancer among women, the main goal of this study was to examine the impact of the Sinopharm and AstraZeneca vaccination on tumor characteristics such as tumor size, important tumor markers, tumorinfiltrating lymphocytes, metastasis to vital organs, and investigation of the PI3K/AKT signaling pathway, and the expression levels of relevant genes (PTEN, mTOR, AKT, PI3K, GSK3, and FoxO1) of the luminal B (MC4L2) mouse model. The tumor size of the mice was measured and monitored every two days, and after thirty days, the mice were euthanized. Remarkably, after vaccination, all vaccinated mice showed a decrease in the size of their tumor and an increase in the number of lymphocytes that had invaded the tumors. Tumor marker levels (VEGF, Ki-67, MMP-2/9), CD4/CD8 ratio, metastasis to vital organs, hormone receptors (ER, PR, and HER-2), and expression of genes related to the advancement of the PI3K/AKT signaling pathway were lower in vaccinated mice. Our research showed that the COVID-19 vaccine can have an anti-cancer effect by slowing the tumor progression and metastasis
