At times over the past year and a half, messenger RNA (mRNA) vaccines have seemed almost like magic. Although the underlying technology was decades in the making, the shots themselves burst onto the scene with eye-watering speed. Less than 12 months after scientists discovered COVID-19, Pfizer-BioNTech and Moderna had each developed mRNA vaccines that were more than 90 percent effective. In countries that could buy large numbers of doses, case counts fell dramatically as inoculations rose. That is why, in our article in Foreign Affairs last spring, we referred to the creation and delivery of these mRNA vaccines as a “medical miracle.”
But over the last few weeks, the emergence of the supertransmissible Omicron variant has shown that even seeming miracles have limits. Although researchers are still racing to figure out just how effective mRNA shots (and all shots) are at preventing illness from Omicron, initial research suggests that the falloff is significant. One study found that two doses of the Pfizer-BioNTech vaccine are 30 percent effective at preventing infection, and a third dose given as a booster increased the effectiveness to 75 percent. (The vaccines still maintain very strong protection against severe illness and death.) Caseloads are rising again across Europe and the United States, and epidemiologists warn that large swaths of the world may soon be inundated with devastating new waves of COVID-19.
