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Well|5 Questions About mRNA Vaccines, Answered
https://www.nytimes.com/2025/05/08/well/mrna-vaccines-safety.html
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We asked experts about how the technology works, its safety and its potential in medicine.
May 8, 2025Updated 6:43 a.m. ET
Health Secretary Robert F. Kennedy, Jr., has repeatedly questioned the safety of mRNA vaccines against Covid-19. Scientists with funding from the National Institutes of Health were advised to scrub their grants of any reference to mRNA. Around the country, state legislatures are considering bills to ban or limit such vaccines, with one describing them as weapons of mass destruction.
While mRNA, or messenger RNA, has received widespread attention in recent years, scientists first discovered it in 1961. They have been studying it and exploring its promise in preventing infectious diseases and treating cancer and rare diseases ever since.
What is mRNA?
A large molecule found in all of our cells, mRNA is used to make every protein that our DNA directs our bodies to build. It does so by carrying information from DNA in the nucleus out to a cell’s protein-making machinery. A single mRNA molecule can be used to make many copies of a protein, but it is naturally programmed to die eventually, said Jeff Coller, a professor of RNA biology and therapeutics at Johns Hopkins University and a co-founder of an RNA therapeutics company.
How do mRNA vaccines work?
Right now, there are three FDA-approved vaccines available that use mRNA, two for Covid-19 and one for R.S.V., or respiratory syncytial virus, in older adults. These vaccines consist of strands of mRNA that code for specific viral proteins.
Say you get a Covid-19 vaccine. The strands of mRNA, packaged into tiny fat particles, go into your muscle and immune cells, said Robert Alexander Wesselhoeft, director of RNA therapeutics at the Gene and Cell Therapy Institute at Mass General Brigham. Protein factories in the cells then take instructions from the mRNA and manufacture a protein like the one found on the surface of a Covid-19 virus. Your body recognizes that protein as foreign, and mounts an immune response.
Most of the mRNA will be gone within a few days, but the body retains a “memory" of it in the form of antibodies, Dr. Coller said. As with other types of vaccines, immunity wanes both over time and as a virus evolves into new variants.
