The primary types of vaccines. Vaccine approaches can be categorized into either whole-cell (left) or subunit (right). Within approaches to whole-cell vaccination, the microbe of interest is attenuated (either by using a related, less virulent microbe that induces crossprotective immunity, or by directed attenuation of the microbe of interest), or killed/inactivated. Alternatively, vaccination can target a specific molecule of the microbe of interest in the case of subunit vaccination. Subunit vaccination can be performed through a variety of techniques, such as by use of recombinant protein or antigen-encoding mRNA LNP. Other vaccine modalities, such as toxoid vaccines (largely similar to native purified [with subsequent inactivation] or monomeric protein [with subsequent inactivation, or genetically inactivated]), protein-conjugate vaccines, and bacterial-vector vaccines are not shown. Figure was created in biorender.com. Holt Lab (2025). https://biorender.com/a6ynx7k