Are mRNA Covid Vaccines Risky? Here’s What the Experts Say

When it became clear in early 2020 that the Sars-CoV-2 virus posed a pandemic threat, researchers who’d been exploring an innovative way to make vaccines saw an opportunity. Experimental messenger RNA vaccines, seen for years as potentially offering speed and flexibility to combat a fast-moving epidemic, were some of the first Covid-19 inoculations to move into human trials. The effort paid off when, late last year, vaccines from Moderna Inc. and the Pfizer Inc./BioNTech SE partnership were the first to demonstrate efficacy. Their performance has raised hopes among scientists that mRNA technology will prove useful against other diseases. Because the platform is so new, however, mRNA vaccines are particularly vulnerable to disinformation campaigns aimed at dissuading people from taking the shots.

Instead of introducing the body to an inactivated or weakened version of a virus or a piece of it, like previous generations of vaccines, they temporarily turn the body’s cells into tiny vaccine-making factories. They do this using synthesized versions of something called messenger RNA, a molecule that normally carries genetic coding from a cell’s DNA to its protein-making machinery. In the case of Covid vaccines, the mRNA instructs the body to make the spike protein that Sars-CoV-2 uses to enter cells. This, in turn, stimulates the body to make high levels of antibodies to the virus. Messenger RNA vaccines are quicker to develop than traditional ones because their production doesn’t require growing viruses or viral proteins inside live cells. It took researchers just a few days in January 2020 to come up with the mRNA sequence used in Moderna’s Covid vaccine.