The coronavirus disease 2019 (COVID-19) pandemic has underscored the importance of mRNA vaccines. The mechanism for how such vaccines work is related to the core biology topic of the central dogma, which students often misunderstand despite its importance. Therefore, we wanted to know whether students can apply their biology knowledge of central dogma to the real-world issue of how mRNA COVID vaccines work. Accordingly, we asked college biology students of different expertise levels how the COVID vaccine worked. Later, we cued them by telling them the vaccine contains mRNA and asked them what the mRNA does. We used thematic analysis to find common ideas in their responses. In the uncued condition, fewer than half of the students used central dogma-related ideas to explain what was in the vaccine or how the vaccine worked. Inaccurate ideas were present among all groups of biology students, particularly entering biology majors and non-biology majors, including the idea that the COVID vaccines contain a weakened, dead, or variant form of the COVID virus. After students were cued, many more students in all expertise groups expressed central dogma-related themes, showing that students could apply the knowledge of central dogma if prompted. Advanced biology majors were much more likely to state that the vaccines code for a viral protein, indicating their advanced application of central dogma concepts. These results highlight inaccurate ideas common among students and show changes in the ability to apply knowledge with student expertise level, which could inform future interventions to support student learning about vaccines and central dogma.