The recent coronavirus disease (COVID-19) forced pre-university professionals to modify the educational system. This work aimed to determine the effects of pandemic situation on students' access to medical studies by comparing the performance of medical students. We evaluated the performance of students enrolled in a subject taught in the first semester of the medical curriculum in two pre-pandemic academic years (PRE), two post-pandemic years (POST), and an intermediate year (INT) using the results of a final multiple-choice exam. Consistency analysis among periods was performed using the Cronbach alpha coefficient ([alpha]), the difficulty index with random effects correction (DI), and the point-biserial correlation index (PB). The five exams were homogeneous and had similar [alpha], DI, and PB difficultness. Performance significantly decreased in POST students compared with PRE students, with a correlation between performance and the academic years (PRE-POST). A significant decrease in the percentage of correct answers was detected in the academic years, with POST students showing lower results than PRE students, but not in the percentage of questions answered incorrectly. Significantly higher percentages of unanswered questions were found among POST students. These results confirm the negative impact of the POST pre-university educational system on the performance of students accessing medical school and suggest that POST students could have a higher degree of uncertainty. Specific education programs should be implemented during the first years of the medical curriculum to tailor this effect and increase students' self-confidence and knowledge, which may be associated with confidence.