Four mRNA vaccines are currently licensed for use in the United States: three for COVID-19 and one for respiratory syncytial virus (RSV). These vaccines use a relatively new approach that delivers genetic instructions to your cells instead of a weakened or inactivated virus. Beyond these approved shots, mRNA technology is being tested for flu, cancer, HIV, and more than a dozen other targets.
Currently Approved mRNA Vaccines
The FDA has licensed the following mRNA vaccines as of early 2026:
- Comirnaty (Pfizer-BioNTech): COVID-19
- Spikevax (Moderna): COVID-19
- mNexspike (Moderna): COVID-19
- mResvia (Moderna): RSV, for adults 60 and older or adults 18 to 59 at higher risk
The three COVID-19 vaccines all target the spike protein on the surface of the coronavirus, though their formulations differ. Spikevax contains 50 micrograms of mRNA per dose, Comirnaty contains 30 micrograms, and the newer mNexspike uses just 10 micrograms. These are tiny amounts, measured in millionths of a gram, but they’re enough to trigger a strong immune response.
mResvia, the RSV vaccine, was the first mRNA vaccine approved for a disease other than COVID-19. In clinical trials, it reduced serious lower respiratory tract disease in older adults by about 79% over the first few months. That protection dropped to roughly 63% by about eight and a half months of follow-up, a pattern similar to what’s seen with other respiratory vaccines.
How mRNA Vaccines Work
Traditional vaccines introduce a weakened virus or a piece of viral protein directly into your body. mRNA vaccines take a different route: they deliver a set of genetic instructions wrapped in a tiny fat bubble called a lipid nanoparticle. Think of the nanoparticle as a protective envelope that keeps the fragile mRNA intact until it reaches your cells.
Once injected, these nanoparticles are absorbed into nearby cells. Inside the cell, the mRNA is released and read by the cell’s protein-building machinery, which follows the instructions to produce a specific viral protein (for COVID-19 vaccines, that’s the spike protein). Your immune system recognizes this protein as foreign, mounts a response against it, and builds memory cells that can fight the real virus if you’re ever exposed. The mRNA itself breaks down within days and never enters the cell’s nucleus or interacts with your DNA.
Common Side Effects
Most people who get an mRNA vaccine experience at least one side effect, and they tend to be more noticeable after the second dose. The most frequently reported reactions from COVID-19 mRNA vaccine trials include injection site pain (reported by roughly 44% to 74% of recipients depending on the study), fatigue, headache, and muscle aches. Fever occurs less often, typically in about 18% of recipients or fewer. These symptoms generally resolve within a day or two and reflect your immune system responding to the vaccine, not an infection.
mRNA Flu Vaccines in Development
Seasonal flu vaccines are one of the most anticipated applications of mRNA technology. Pfizer has already completed a Phase 3 trial of a quadrivalent (four-strain) mRNA flu vaccine in adults 18 and older. The potential advantage over conventional flu shots, which are grown in eggs or cell cultures over several months, is speed. mRNA vaccines can be designed and manufactured much faster, which could allow manufacturers to match circulating strains more precisely each season. Moderna is also developing mRNA flu candidates, including combination vaccines that target both flu and COVID-19 in a single shot.
mRNA Cancer Vaccines
Some of the most striking mRNA research is happening in cancer treatment. These aren’t preventive vaccines like a flu shot. Instead, they’re therapeutic, designed to train your immune system to recognize and attack cancer cells that are already present.
The most advanced example is an experimental personalized melanoma vaccine developed by Moderna. In the KEYNOTE-942 trial, patients with high-risk melanoma who had their tumors surgically removed received this custom vaccine alongside an immunotherapy drug. At three years, 74.8% of patients in the vaccine group remained cancer-free, compared to 55.6% in the group receiving immunotherapy alone. That translates to nearly a 50% reduction in the risk of the cancer coming back or causing death. The vaccine is personalized: each patient’s tumor is sequenced, and the mRNA is tailored to target proteins unique to that individual’s cancer.
BioNTech is taking a slightly different approach with BNT111, an “off-the-shelf” mRNA vaccine that targets four proteins commonly found across many melanomas. Combined with an immunotherapy drug, it showed meaningful response rates in patients with advanced melanoma that couldn’t be surgically removed. The FDA granted it Fast Track designation, which speeds up the review process.
Other Diseases in the Pipeline
At least 12 mRNA vaccines for infectious diseases beyond COVID-19 are now in human clinical trials. The list covers a wide range of targets: cytomegalovirus (CMV), Epstein-Barr virus, HIV, Zika, Nipah, rabies, chikungunya, shingles (varicella-zoster), and several respiratory viruses including human metapneumovirus and parainfluenza. Some of these diseases have no approved vaccine at all, making mRNA a particularly promising path. CMV, for instance, infects most adults and can cause serious birth defects when contracted during pregnancy, yet no vaccine currently exists for it.
Not all of these candidates will succeed. But the speed and flexibility of mRNA manufacturing, proven during the COVID-19 pandemic, has made the technology a leading platform for vaccine development in a way that would have been hard to imagine a decade ago.