The seasonal influenza vaccine is a standardized public health measure taken annually to reduce the spread and severity of the flu. Following the widespread use of new vaccine platforms, many people question the technology behind their routine immunizations. Specifically, there is interest in whether the current flu shot utilizes the messenger RNA (mRNA) technology seen in some recent vaccines. This article provides a direct answer and explores the established and emerging science involved in creating influenza protection.
Current Flu Vaccines Do Not Use mRNA
Current seasonal influenza vaccines do not rely on messenger RNA technology. These shots utilize established, non-mRNA platforms that have been in use for many years to induce an immune response. The active components are either inactivated (killed) whole viruses, weakened live viruses, or specific purified proteins from the virus. The yearly influenza shot is based on traditional vaccine science, not the newer mRNA mechanism.
How Traditional Flu Vaccines Are Made
The vast majority of seasonal flu shots are manufactured using one of three proven, non-mRNA methods. The most common technique is the egg-based process, which has been the standard for over 70 years. This method involves injecting selected influenza virus strains into fertilized chicken eggs, where the viruses replicate over several days. The virus-containing fluid is then harvested, inactivated, and purified before being formulated into the final vaccine.
A second approach is the cell-based method, which grows the virus in cultured mammalian cells instead of eggs. This process starts by inoculating the cultured cells with the selected vaccine viruses, allowing them to replicate in a controlled environment. The viral material is then harvested, inactivated, and purified for use in the vaccine. Because this process is entirely egg-free and the virus does not have to adapt to grow inside chicken eggs, the resulting vaccine component may be a closer match to the circulating wild-type virus.
The third technology is the recombinant protein-based method, which avoids using the whole virus entirely. Scientists identify the gene that codes for the surface protein, Hemagglutinin (HA), which the immune system recognizes. This gene is combined with a portion of another virus that grows well in insect cells. These cells act as tiny factories to produce large quantities of the HA protein. This purified, genetically engineered protein is the sole active ingredient, eliminating the need to grow the flu virus itself.
The Basics of mRNA Technology
Messenger RNA, or mRNA, functions as a set of temporary instructions that cells use to build proteins. In a vaccine context, the mRNA molecule is synthetically created in a lab to carry the blueprint for a specific viral protein, such as the influenza Hemagglutinin. The mRNA is encapsulated within tiny lipid nanoparticles, which protect the fragile molecule and help it enter the body’s cells. Once inside the cell’s cytoplasm, the cell’s machinery reads these instructions and begins producing the viral protein.
The body’s immune system detects this newly produced, harmless protein and mounts a defensive response, creating antibodies and specialized T-cells. This process teaches the immune system how to recognize and fight the actual virus if encountered later. Importantly, the mRNA never enters the cell nucleus, which is the location of the body’s own DNA. The instructional mRNA is short-lived and is quickly broken down by the body once its job is complete.
Research into mRNA Flu Shots
While current seasonal vaccines do not use this technology, major pharmaceutical companies are invested in developing mRNA-based influenza shots. This research is currently in various phases of clinical trials, with some candidates testing single-strain protection and others evaluating multivalent vaccines that target multiple strains at once. The primary promise of this platform for influenza is the potential for significantly faster manufacturing compared to traditional methods.
The ability to rapidly produce a vaccine is particularly valuable when circulating flu strains differ from those predicted months earlier. An mRNA platform could allow manufacturers to better match the vaccine to the dominant strains, potentially leading to greater effectiveness each year. Researchers are also exploring whether mRNA vaccines can induce a broader and more potent immune response against the constantly changing influenza virus. Future seasonal vaccines may transition to using mRNA technology due to these potential benefits.