https://phys.org/news/2019-01-dna-origami-precise-tool-optimal.html

Today, many new vaccines make use of something called "particle display," which means that the antigens are introduced into the body and presented to the immune system in the form of particles with lots of antigens densely packed on the surface. In some cases, particle display of antigens works better as a vaccine than simply providing free antigens; one example is the HPV vaccine, which protects against cervical cancer.

Antibodies, or immunoglobulins, perhaps the most important part of the body's defence against infection, bind antigens very effectively. The antibodies have a Y-shaped structure whereby each "arm" can bind an antigen. In this way, each antibody molecule can usually bind two antigen molecules.