As of mid-2025, there are four mRNA vaccines approved for use in major markets worldwide, with more than 120 additional mRNA-based therapies and vaccines in clinical trials. The approved vaccines target two diseases: COVID-19 and respiratory syncytial virus (RSV). But the technology is expanding fast, with candidates in development for influenza, cancer, and several other conditions.
Approved mRNA Vaccines
The U.S. Food and Drug Administration has licensed three mRNA vaccines for COVID-19: Comirnaty (made by Pfizer-BioNTech), Spikevax (Moderna), and a newer entry called Mnexspike. All three use the same core approach: a strand of messenger RNA wrapped in a tiny fat-based shell called a lipid nanoparticle, which protects the fragile mRNA and helps it enter your cells. Once inside, your cells read the mRNA instructions and produce a piece of the virus’s spike protein, training your immune system to recognize the real thing.
The fourth approved mRNA vaccine marked a major milestone. In May 2024, the FDA approved Moderna’s mRESVIA, the first mRNA vaccine for a disease other than COVID-19. It protects against RSV, the respiratory virus that causes serious lung infections in older adults. mRESVIA is approved for adults 60 and older, and for adults 18 to 59 who are at higher risk for severe RSV illness.
Globally, the picture is slightly different. The World Health Organization has prequalified Comirnaty for international use, while Spikevax was delisted from the WHO’s prequalification list in October 2024. Japan has gone a step further by approving a fifth mRNA vaccine: Kostaive, made by CSL and Arcturus Therapeutics. Approved in November 2023, it became the world’s first self-amplifying mRNA vaccine, a newer variation of the technology.
How Self-Amplifying mRNA Differs
Standard mRNA vaccines deliver a set amount of genetic instructions into your cells. Once those instructions are read, they’re used up. Self-amplifying mRNA (sometimes called saRNA) includes extra code that lets the mRNA copy itself inside your cells, producing more of the target protein from a smaller initial dose. Think of it as a message that photocopies itself before it’s discarded.
Japan’s approval of Kostaive for COVID-19 was the first real-world test of this approach. No self-amplifying mRNA vaccine has yet been approved by the FDA or the European Medicines Agency, but the technology is being explored for several other diseases.
mRNA Flu Vaccines in Testing
Seasonal influenza is one of the most anticipated targets for mRNA technology, and early trial results have been striking. In a Phase 2 trial, Pfizer tested its mRNA-based flu vaccine by exposing vaccinated volunteers to a live H1N1 influenza virus under controlled conditions. None of the participants who received the mRNA vaccine developed symptomatic flu, compared to 4.2% in the group that received a traditional flu shot and 26.9% in the unvaccinated control group. That translates to 100% effectiveness for the mRNA version versus about 85% for the standard vaccine in that controlled setting.
The mRNA vaccine also crushed viral replication more effectively. Participants who received it had dramatically lower viral loads than those given the traditional shot. These are early-stage results in a small, controlled trial with young, healthy adults, so the numbers will likely shift in larger real-world studies. But they suggest mRNA flu vaccines could outperform the conventional shots that have to be reformulated and manufactured from scratch each year. Because mRNA vaccines can be updated by simply swapping out the genetic sequence, they could potentially be produced faster and matched more precisely to circulating strains.
Cancer Vaccines in Development
Perhaps the most ambitious frontier for mRNA is cancer treatment. Unlike traditional vaccines that prevent infection, mRNA cancer vaccines are designed to treat existing tumors by teaching the immune system to attack cancer cells. The most advanced candidate is mRNA-4157, a personalized vaccine made by Moderna that is custom-built for each patient based on the specific mutations in their tumor. It’s currently in a Phase 3 trial spanning 26 countries across six continents.
A broader international effort called the Cancer Vaccine Launch Pad aims to fast-track thousands of patients into trials for mRNA treatments targeting lung, breast, and head and neck cancers, among others. These are therapeutic vaccines, not preventive ones, so they’d be given after a cancer diagnosis rather than before.
The Full Pipeline
Beyond flu and cancer, the mRNA pipeline covers a wide range of diseases. More than 120 clinical trials involving mRNA-based therapies are currently underway, including multiple Phase 3 trials. Targets under investigation include HIV, Zika, cytomegalovirus (a common virus that can cause birth defects), Epstein-Barr virus (linked to multiple sclerosis and certain cancers), and various tropical diseases.
Some of these programs use mRNA not as a vaccine at all but as a way to deliver therapeutic proteins directly into the body, essentially turning your own cells into temporary drug factories. This approach is being tested for rare genetic conditions, autoimmune diseases, and heart failure.
So the short answer: five mRNA vaccines are approved globally right now, four of them for COVID-19 and one for RSV. But the technology has moved well past its pandemic origins, with over a hundred candidates working their way through clinical testing for diseases that have never had effective vaccines before.