Background: According to results of previous ACHOC-C19 study, mortality in patients with cancer and COVID 19 infection in Colombia is 26%. The impact of vaccination was not evaluated prior to the implementation of this strategy worldwide in patients with cancer. We aimed to characterize SARSCOV 2 infection in a local cohort of vaccinated oncologic patients. Methods: The ACHOCC-19 VAC registry is a national multi-center observational cohort study. Data were collected between April 2021 and March 2022. Inclusion criteria were: age more than 18 years, confirmed diagnosis of cancer (solid tumors), be receiving treatment or being followed-up and have received at least one dose of COVID-19 vaccine. 11 oncologists from 10 health institutions participated. The primary outcome was 30 days mortality due to COVID 19 infection. Secondary outcome was to describe adverse effects related to vaccination. A descriptive univariate and inferential analysis were performed. Results: 720 patients were included, average age was 60 years, 91% lived in urban areas, 12% had low income. 73% (525) were women. The most frequent diagnosis were: breast cancer 47% (338), prostate cancer 7% (50) and lung cancer 4.6% (36). ECOG 0-1 and 2 in 91.7% and 6.1% of population respectively. 41.40% had no comorbidities and 59.4% had 1 or more comorbidity. 29.1% presented metastatic cancer, 59.3% were receiving oncological treatment of which, 32.7% were neoadjuvant or adjuvant and 28.6% palliative. 31.66% were being followed up without treatment. 32.6% had stable disease and 5.9% had cancer in progression. Administered vaccines were CoronaVac (40%), BNT162b2 (35%) others 25%, in accordance with initial availability of vaccines for oncologic population in Colombia. 93.9% of population received 2 doses. COVID19 infection was acquired by 35.9% of the population, 30 days mortality due to infection was 3%. Table 1. Frequency of adverse effects with first and second dose were 14.8% and 12.2%, mild intensity in 93% and 100% respectively, being myalgias (5%), arthralgias (2-3%) and fever (3.5%) the most frequent. Conclusions: In our population, the efficacy of the vaccine against COVID 19 is consistent with available reports in the scientific literature. The incidence of 30 days mortality due to SARCOV 2 infection is very low. Vaccine-related adverse effects had frequency of less than 15% and mild intensity. These findings reinforce the need to promote and intensify vaccination in the oncologic patients.