mRNA Vaccine Safety, Development Explained As Biden Mandates COVID Shots

On Thursday, President Joe Biden announced a wide-reaching federal vaccine mandate, in a bid to get millions more Americans immunized in order to squash the country's COVID outbreak.

The president said the new mandate, which could affect as many as 100 million U.S. citizens, came in response to the surging Delta variant, as well as the vast number of people in the country who are unvaccinated. He said that people's refusal to get a vaccine "has cost all of us."

Vaccine hesitancy has prevented some from getting a shot while COVID spreads across the country. So what are mRNA vaccines—the type of COVID vaccine made by Pfizer and Moderna—and are they safe?

How mRNA vaccines work

mRNA vaccines work slightly differently to those that have come before. Many vaccines feature a weak or inactive version of a germ that is injected into the body, teaching the immune system to fight against it in future without it bearing the brunt of a proper infection.

mRNA vaccines do not work that way. Instead, they make use of mRNA, or messenger RNA, which is a crucial set of instructions that tell our cells how to produce proteins, which are necessary for our body to function. Our cells use mRNA all the time.

The mRNA COVID vaccines contain instructions that tell our cells to produce a protein associated with a little bit of the virus' spike protein, which lies on the outside of the virus.

On its own, this spike is harmless. But our bodies still recognize it as something that shouldn't be there, so the immune system prepares a response, and remembers that response for when a real infection occurs.

How long have mRNA vaccines been in development?

The emergency authorization of the Pfizer vaccine back in December marked the first time in history that an mRNA vaccine had been authorized for human use. But mRNA vaccine technology has been in development for decades.

Hungarian-born scientist Katalin Karikó, who came to the U.S. in the 1980s with the idea of using mRNA to produce proteins in the body at will, is often cited as a major figure in the development of the technology.

She hit dead ends in her research until she partnered with Dr. Drew Weissman at the University of Pennsylvania, who was interested in developing an mRNA HIV vaccine. The two found that modified mRNAs could produce proteins without causing undesirable side effects. They first published their findings in 2005.

Companies then started to recognize the potential of mRNA vaccine technology. Moderna, which had its own COVID vaccine authorized shortly after Pfizer's, was founded in 2010 for the sole purpose of producing mRNA vaccines.

Are mRNA vaccines safe?

Over 175 million U.S. citizens have now had a COVID vaccine—the vast majority of which were mRNA types. The COVID mRNA vaccines went through the same rigorous safety testing as all vaccines do before the FDA deemed them safe for emergency use or approval, according to the CDC.

Dr. Michel Goldman, chief editor of the Frontiers in Medicine journal and a professor of immunology at the Université Libre de Bruxelles in Belgium, pointed to the technology's years of development as proof that mRNA vaccines are safe, including human trials of mRNA technology to treat cancer since 2011.

He told the European Commission's Horizon magazine: "If there was a real problem with the technology, we'd have seen it before now for sure."

Goldman said the idea that mRNA vaccines could change people's DNA—a concern that has been circulated regarding the vaccines— is "completely false," as the mRNA never reaches the nucleus of cells where DNA is stored.

No COVID vaccines, including the mRNA shots, can cause a person to catch or develop the disease.

Vaccine trials, the massive clinical tests that vaccine manufacturers are federally required to carry out in order to prove their products are safe, provide further proof that mRNA shots are safe.

In general, most vaccine side effects appear within the first two months of a person having a shot, meaning most issues would have shown up in the trials.

Pfizer's Phase 3 trial alone involved around 40,000 people and began in July 2020. Pfizer said it identified "no specific safety concerns" and that the most common reactions were injection site reactions, tiredness, headache, and muscle pain, among others.

The CDC and FDA continue to monitor vaccine safety even after approval, including by using what is known as the Vaccine Adverse Event Reporting System (VAERS).

mRNA COVID vaccines have been linked to rare cases of types of heart inflammation called myocarditis and pericarditis in male adolescents and young adults, according to the CDC. Most patients quickly recovered.

COVID, on the other hand, has killed 4.55 million people, including children and adults. The CDC recommends those eligible get vaccinated as soon as possible.

COVID vaccine
A COVID vaccine dose is prepared at a vaccination center in Cardiff, U.K., in December 2020. mRNA technology has been in development for many years. Justin Tallis/AFP / Getty