https://www.nature.com/articles/d41586-021-00019-w
Advances in the technology are now helping researchers to close in on some of the holy grails of vaccine development — such as a universal flu shot that would work against any strain of the virus without being redesigned each year. Others are eyeing jabs against HIV and other top killers in lower-income countries. Such vaccines have eluded scientists often because of the way that pathogens systematically alter their surface proteins to evade immune recognition. Some infectious agents, such as malaria, also have elaborate life cycles that further complicate the process of picking antigens.
RNA vaccines could include instructions for multiple antigens, either strung together in a single strand, or with several RNAs packaged together in a single nanoparticle.