Coronavirus proteins are injected directly into the body. Fragments of proteins or protein shells that mimic the coronavirus’s outer coat can also be used.

Two types of vaccines:

Protein subunits: Most of these vaccines are focusing on the virus’ spike protein, or a key part of it called the receptor binding domain. In order to work, these vaccines might require multiple doses and also adjuvants (immune-stimulating molecules delivered alongside the vaccine). Vaccines against the SARS virus have been developed in this way for protecting monkeys, but they haven’t been tested in people.

Virus-like particles: These vaccines use empty virus shells to mimic the coronavirus structure, but they aren’t infectious, as they lack genetic material. They can trigger a strong immune response, but can be difficult to manufacture.