We designed and evaluated a student laboratory workshop on plant-based vaccines against the SARS-CoV-2 virus. The workshop focused on hands-on laboratory techniques, including DNA extraction from rice seeds, where the recombinant protein was produced, detection of the transgene, and basic concepts on how vaccines work in the human body to offer immunity against viral diseases. We developed a robust science activity to support scientific inquiry learning and to provide a more in-depth understanding of science topics. The 14-hour learning experience was a component of a large research and outreach programme, "IlerCOVID Project." A total of 129 secondary school students (grades 11 and 12) from eight different secondary schools participated in the study. Data were collected through pre-post questionnaires on students' knowledge about genetic engineering, laboratory techniques and immunology. Based on data collected, results show that this approach enhanced substantially the students' knowledge on the topics covered in the workshop, although a control group would be necessary to confirm the effectiveness of the designed activity. We conclude that the students improved their knowledge of biology, allowing them to have more informed science-based views on the technology underpinning vaccines and their benefits.