Yesterday I attended the Rose Cafe on engineering vaccines. Even though I am an engineering student, I have not taken a biology course since my freshman year of high school, so the extent of knowledge that I came in with on the immune system was approximately, “There are these things called T-cells, which do something to help fight off infections.” Fortunately, GRF Tyler’s presentation did not require much more knowledge than that. I had done some research on vaccines for a project later on in high school, so I knew about the three main types of vaccines: live-attenuated, inactivated, and subunit vaccines. While I understood that the third type involved using cell parts, I did not really understand how it worked before attending the cafe. In particular, I never would have considered the importance of sugars on the surface of cells, and that certain sugars can cause an immune response. I also never really understood why booster shots are needed for some types of vaccines, but not others. Apparently it is because some vaccines are better at causing a response from the T-cells, which is necessary for long-term immunity. So the key to effective vaccines is not just causing an immune response, but more specifically causing a T-cell response. In fact, sometimes–such as the attempts to make a vaccine out of sugar alone–the immune system (in particular, B-cells) responds so quickly and efficiently that the T-cells have no need to respond. That was never a problem that I would have considered existing.