The seasonal flu shot protects against the influenza virus. Public discussion surrounding vaccine technology has increased interest in how these shots are manufactured and what they contain. The introduction of messenger RNA (mRNA) technology for COVID-19 vaccines has led many to question whether this newer method is also present in the seasonal flu shot. Understanding the different technological approaches clarifies what the flu vaccine contains and how it works.
The Current Answer on Flu Vaccines
Standard, currently approved seasonal influenza vaccines do not contain mRNA technology. These vaccines rely on older, well-established methods used for decades to stimulate the immune system. None of the currently available flu shots, including the injected forms and the nasal spray version, utilize a messenger RNA molecule as the active ingredient.
Seasonal flu vaccines are primarily based on three conventional technologies: inactivated influenza vaccines, live attenuated influenza vaccines, and recombinant protein vaccines. The standard flu shot is manufactured using these conventional platforms.
The Traditional Approach to Immunity
Conventional flu shots introduce a harmless piece of the influenza virus to the body, prompting an immune response without causing illness. The most common form is the inactivated influenza vaccine (IIV), which contains virus particles that have been completely killed. These are processed into a “split” or “subunit” vaccine containing fragments of surface proteins, such as hemagglutinin (HA) and neuraminidase (NA). The body recognizes these proteins as foreign antigens and produces antibodies tailored to neutralize the live virus later.
The recombinant influenza vaccine (RIV) uses a different manufacturing process. This method bypasses the need to grow the virus in eggs or cell culture. Scientists identify the gene sequence for the HA surface protein and insert it into a system that rapidly produces large quantities of the purified protein, which is then administered to trigger the immune response.
A third type is the live attenuated influenza vaccine (LAIV), a nasal spray containing weakened live viruses. These viruses can replicate in the cooler nasal passages but not in the lungs. These traditional approaches introduce the actual viral protein or a fragment of the virus itself to the immune system, rather than requiring the body’s cells to manufacture the protein internally.
Understanding the mRNA Process
In contrast, the mRNA process does not introduce any part of the actual virus. An mRNA vaccine delivers a synthetic strand of messenger RNA to the body’s cells. Messenger RNA is a natural molecule that acts as instructions for making proteins. The vaccine’s mRNA carries the code for a distinctive viral protein, such as the influenza virus’s hemagglutinin protein.
Once the mRNA is delivered, the cell’s internal machinery reads the instructions and temporarily produces the viral protein. This protein is then displayed on the cell’s surface, where the immune system detects it as foreign. The immune system responds by producing protective antibodies and specialized T-cells, training the body to recognize and fight the real virus.
The mRNA never enters the cell’s nucleus, where the host DNA is stored. The molecule is fragile and quickly breaks down after the protein is made, leaving no permanent change to the cell’s genetic material. This method leverages the body’s own protein-making capabilities to generate the necessary antigen for immunity.
Research Status of mRNA Flu Technology
While currently approved flu shots are not mRNA-based, this technology is actively being researched and developed for future influenza vaccines. Major pharmaceutical companies are conducting clinical trials, with some candidates progressing through Phase 3 studies. Early results suggest that some mRNA vaccine candidates may elicit superior immune responses or better efficacy against symptomatic illness compared to current standard vaccines.
A significant advantage of the mRNA platform is the speed of manufacturing, which could drastically reduce the six-month timeline required for traditional production. This faster turnaround time allows manufacturers to better match the specific flu strains circulating each season, potentially improving overall effectiveness. The technology also offers flexibility, making it easier to rapidly adjust the vaccine content to target multiple strains or quickly respond to a new pandemic threat. These candidates must complete all necessary regulatory approvals before being deployed for widespread use.