mRNA vaccines are not new. The technology behind them has been in development for over three decades, with roots stretching back to the discovery of mRNA itself in 1961. The COVID-19 vaccines from Pfizer and Moderna were the first mRNA vaccines to receive widespread authorization, but they were built on a foundation of research that began in the late 1980s and included human clinical trials years before the pandemic.
mRNA Research Began in the Late 1980s
The molecule at the center of these vaccines, messenger RNA, was first identified in 1961 by Sydney Brenner, François Jacob, and Matthew Meselson. They discovered that mRNA carries instructions from DNA to the cell’s protein-building machinery. For decades, that knowledge stayed largely in the realm of basic biology.
The idea of using mRNA as a therapeutic tool took off in 1989, when a biotech startup called Vical Incorporated published early successes with the concept. By 1990, the first proof-of-concept animal study showed that lab-made mRNA injected into a living organism could produce proteins. That was the key insight: if you could get synthetic mRNA into cells, those cells would follow its instructions and build a specific protein, which could then train the immune system to recognize a virus.
The first mRNA vaccine followed in 1993. It used mRNA encoding a protein from the influenza virus, wrapped in simple fat-based particles called liposomes. In mice, it triggered virus-specific immune responses. From that point forward, researchers spent years tackling two stubborn problems: mRNA was fragile and broke down too quickly, and the immune system tended to destroy it before it could do its job.
Human Trials Started Before COVID-19
The first human clinical trial of an mRNA vaccine began in October 2013, more than six years before the pandemic. Researchers tested a rabies mRNA vaccine in 101 healthy adults between 2013 and 2016. The trial demonstrated that a prophylactic mRNA vaccine could induce functional antibodies against a viral target in humans, a milestone that proved the platform could work in people, not just lab animals.
Meanwhile, mRNA cancer vaccines were also being explored. Researchers had been studying mRNA-based immunotherapy for cancer since the early 1990s, aiming to teach the immune system to recognize and attack tumor cells. By the time COVID-19 arrived, mRNA technology had roughly three decades of development behind it.
How mRNA Vaccines Differ From Traditional Ones
Traditional vaccines typically introduce a weakened virus, an inactivated virus, or a piece of viral protein directly into the body. Viral vector vaccines use a harmless virus (often an adenovirus) to carry genetic instructions into your cells, where those instructions are read in the nucleus to produce an antigen.
mRNA vaccines skip the middleman. They deliver a short, synthetic strand of genetic code wrapped in a tiny fat particle. Once inside your cells, the mRNA is read by your cell’s own protein-building equipment to produce a specific viral protein, like the spike protein of SARS-CoV-2. Your immune system then recognizes that protein as foreign and mounts a defense. The mRNA never enters the cell nucleus and cannot integrate into your DNA.
This design has a practical advantage: because the mRNA is made synthetically, manufacturing can happen in weeks rather than the months or years required to grow viruses in cell cultures or produce purified proteins.
Why COVID-19 Vaccines Came So Fast
The speed of the COVID-19 mRNA vaccines surprised many people, but it wasn’t a case of starting from scratch. Researchers at the National Institutes of Health and Moderna had spent years studying a related coronavirus, MERS, as a “prototype pathogen.” That work produced a generalizable strategy for stabilizing coronavirus spike proteins in a shape the immune system could easily recognize.
When the genetic sequence of SARS-CoV-2 was published on January 10, 2020, researchers applied their pre-existing design within 24 hours, swapping in the new virus’s spike protein sequence without needing additional lab experiments. Within five days, manufacturing of what would become the Moderna vaccine (mRNA-1273) had begun. The first human received a dose on March 16, 2020, just 66 days after the viral sequence was released.
This timeline was possible because the mRNA platform functions like a template. The delivery system and manufacturing process stay the same; only the genetic instructions change. Years of prior work on coronaviruses, lipid nanoparticle delivery, and mRNA stability meant that when a new threat appeared, the technology was ready.
What Happens to mRNA in Your Body
Synthetic mRNA was originally expected to break down within a few days, based on animal studies and the natural fragility of RNA molecules. Clinical data from COVID-19 vaccines show a somewhat longer timeline: modified mRNA can persist up to about 30 days in lymph nodes and nearby tissues. The spike protein produced from that mRNA has been detected in blood for up to roughly six months in some studies. After that, both the mRNA and the protein are cleared. The mRNA does not become a permanent part of your cells or alter your genetic code.
mRNA Vaccines in Development Now
COVID-19 was the proof of concept at a global scale, and now the same platform is being applied to other diseases. Several mRNA vaccines are in late-stage clinical trials:
- Influenza: Both Moderna and Pfizer have Phase 3 trials for mRNA flu vaccines, aiming to improve on the traditional egg-grown flu shots that must be reformulated each year.
- RSV (respiratory syncytial virus): Moderna’s RSV vaccine is in Phase 2/3 and Phase 3 trials, targeting a virus that is particularly dangerous for infants and older adults.
- CMV (cytomegalovirus): Moderna has multiple Phase 2 and Phase 3 trials for a vaccine against this common virus, which can cause serious birth defects when contracted during pregnancy.
- Zika: A Phase 2 trial is active for Moderna’s Zika mRNA vaccine.
Cancer immunotherapy remains an active area as well. Researchers are developing personalized mRNA vaccines that encode proteins specific to an individual patient’s tumor, training their immune system to target cancer cells. This line of work predates the pandemic by decades but has been accelerated by the manufacturing and delivery advances that COVID-19 vaccines validated at scale.