Background and objectives: Since the introduction of the COVID-19 vaccine through the National COVID-19 Immunization Program in Malaysia in February 2021, the number of cases of severe COVID-19 and mortality have progressively decreased. We explored the association between vaccination status, type of vaccine, and the highest COVID-19 clinical category. Methods: Patients were recruited via the electronic medical record (EMR) at University Malaya Medical Centre (UMMC) from July 2021 onward. Included patients were aged ≥18 years old with positive SARS-CoV-2 RT-PCR results from respiratory samples (naso-oropharyngeal swab, saliva, or sputum). Patient demographic data, COVID-19 clinical category, vaccination status, and type of vaccine received were recorded. Results: In total, 1,391 positive SARS-CoV-2 PCR results were reviewed; 1,188 patients (85%) with complete data were analyzed. These patients’ median age was 50 years. The proportions of patients COVID-19 clinical categories were as follows: category 1 (4.04%), category 2 (28.37%), category 3 (10.7%), category 4 (30.6%), and category 5 (2.6%). The mortality rate was 21.5%. As of July 2021, only 16.8% of patients were fully vaccinated, 30.3% were vaccinated, 31.5% unvaccinated, and 21.5% had unknown vaccination status. In total 364 patients with category 4 COVID-19 (4.4%; P < .001) were fully vaccinated and no patients who were fully vaccinated had category 5 COVID-19 (P = .011). Furthermore, 40.8% of patients who died had unknown vaccination status (P < .01); 28.1% of patients who died were unvaccinated (P = .015); 25.3% of patients who died were partially vaccinated (P = .036); and 0.4% of patients who died were fully vaccinated (P < .001). For category 4 and 5 illness and death, there were no significant differences between the type of vaccine received (Pfizer-BioNTechR, Astra ZenecaR and Coronavac/SinovacR) and severe COVID-19. Conclusions: The completion of 2 doses of government-approved COVID-19 vaccination is paramount in preventing severe COVID-19 disease and death. Rapid rollout and equitable distribution of vaccination should be initiated. Vaccine hesitancy should be promptly addressed to ensure vaccination uptake.