Vaccines work by imitating infection to encourage the body to produce antibodies against infectious agents. In doing so, the body’s immune system adds to its memory, so if the body ever encounters the same infectious agent again, it is ready to fight it off.
There are several different types of vaccines. The most effective ones produce long-lasting immunity. Live attenuated vaccines, in which the infectious agent is alive but weakened, closely mimic natural infection and therefore produce a strong immune response. Subunit vaccines, which are generated from parts of the infectious agent (often surface proteins) that stimulate an immune response, generally produce long-lasting immune protection. Likewise, DNA vaccines, which contain one or more segments of the infectious agent’s genetic material, are associated with long-lasting immunity. In DNA vaccines, cells use genetic information to produce the immune-stimulating proteins. DNA vaccines are relatively inexpensive and simple to produce. RNA vaccines, consisting of mRNA (messenger RNA), are similarly cheap and easy to produce. RNA vaccines were quickly developed and used to help stop the spread of COVID-19 during the global pandemic.