Much of the news about vaccines to combat the pandemic emphasizes speed: a “race” to approval, “Operation Warp Speed” and the truly record-breaking timelines. But speed is not the only remarkable aspect of the process that will soon result in vaccines reaching tens of millions of Americans. The first two that are expected to receive emergency use authorization from the Food and Drug Administration, from Pfizer and Moderna, rely on an extraordinary advance in technology, never before used on such a scale, with great promise for the future, and some uncertainties.
In the past, vaccines were largely based on an inactivated or weakened form of a pathogen that was used to train the body’s immune system to fight an infection. Such vaccines have been remarkably successful in fighting diseases such as measles and polio, but they have also taken many years and sometimes decades to develop.
By contrast, the pair of new vaccines rely on a tiny piece of synthesized genetic material known as messenger RNA. In nature, mRNA serves to convey instructions inscribed in DNA and deliver them to the protein-making parts of a cell. The new vaccines use the synthesized mRNA to deliver instructions to the cell to produce the spike protein that the coronavirus uses to latch on to a cell and infect it. When the spike proteins are produced by the cell — on instruction from the mRNA — they then train the body’s immune system to go after them.