This shed some light on your observations.
Making “Edible Vaccines” in Plants
Some scientists believe that vaccines could be produced in edible plants, such as bananas or potatoes, which would then provide the delivery vehicle. This approach would yield vaccines that are needle-free and require no adjuvants, chemicals that stimulate the immune response. When the plant is ingested, the plant cell walls would protect the vaccine antigens from degradation by stomach acid and digestive enzymes. Then in the intestine, the antigens would be released and transported into the circulatory system. Edible vaccines would stimulate both mucosal and systemic immunity, providing a higher level of protection than traditional vaccines.
https://biosecurity.fas.org/education/dualuse-agriculture/2.-agricultural-biotechnology/making-edible-vaccines-in-plants.html
Vaccines in your tomatoes, bananas or lettece.