A single vaccine has been shown to protect people against both SARS-CoV-2 and influenza viruses - and with greater effectiveness than vaccines targeting just one or the other, pharmaceutical company Moderna has announced.

Moderna, based in Cambridge, Massachusetts, announced earlier this month announced that it had successfully completed Phase III clinical testing for the drug, which, like the company's pioneering COVID-19 vaccines, is based on mRNA. In a statement to its investors, Moderna said the vaccine was more effective at protecting immunity in adults over 50 than competing flu and COVID-19 shots.

Moderna now plans to seek approval from the US Food and Drug Administration (FDA) to bring the vaccine to market.

Combination vaccines can have significant health benefits, but are often time-consuming and expensive to develop. Moderna's latest rapid success shows that RNA can help overcome some of these difficulties, says James Thaventhiran, a clinical immunologist at the University of Cambridge, UK. “This is a great example of why the technology is exciting,” he says, adding that the combination vaccines using mRNA are “just the beginning” for RNA technology.

The RNA effect

Vaccinations help people build immunity against a disease by exposing their immune cells to an antigen, such as an antigen. B. expose to a protein, a DNA snippet or even an entire pathogenic organism that has been inactivated. If the real pathogen appears, the immune system can quickly recognize the threat and mount resistance.

Creating antigens is a difficult process, and combining different antigens in a vaccine further increases its complexity. "It sounds like it should be so easy, right? You just mix them together," says Jacqueline Miller, a pediatrician and head of infectious disease development at Moderna. “But it’s actually much more complicated than developing individual components.”

The chemical components that make up single-target vaccines can sometimes react with each other when combined, risking making each drug less effective. However, mRNA-based vaccines do not face such an obstacle because the drug components tend to be the same for different antigens.

mRNA is a molecule made of nucleic acids, and its main function is to tell cells which proteins to make. mRNA-based vaccines inject mRNA into cells to create copies of antigens for the immune system to recognize. The result is a strong immune response based on drug components that do not compete with each other - even if they target different pathogens.

That could explain why the risk of combination vaccines being ineffective is "clearly" not a problem with the new COVID influenza vaccine, Thaventhiran says, since the shot appears to boost immunity more than single shots do.

The vaccine's code can also change quickly to keep pace with evolving variants. One of the problems with current non-mRNA influenza vaccines is that the antigen is grown in chicken eggs, a process that takes six months. During this time the virus can mutate and change. In contrast, "with RNA, it literally takes weeks to make a new variant," says Drew Weissman, an immunologist at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia.

Modern mRNA immunization

Researchers have tested the limit on the number of antigen instructions they can fit into an mRNA vaccine; one group packed mRNA instructions for all 20 variants of influenza into a lipid layer. Moderna hopes so respiratory syncytial virus (RSV) – which causes cold-like symptoms – as a third pathogen to add to its current COVID-influenza pair.

For most people, FDA approval of the Moderna shot means "a trip to the pharmacy," Weissman says. “One vaccination will be enough to protect you from both the flu and COVID.”

COVID-19 booster uptake has declined in the United States since the first rounds of vaccinations. According to the U.S. Centers for Disease Control and Prevention, about 47% of adults have received the flu shot as of the beginning of this year. Combining vaccinations could help ensure more people are protected from COVID-19, Miller says.

And looking to the future, mRNA combination vaccines could help reduce the burden of vaccinations on parents of young children. Infants are currently the primary target groups of available combination vaccines, but still receive multiple rounds of vaccinations in the first few years of life. “Parents would be thrilled” to reduce the number of shots their children have to get, Weissman said. Just a few shots — which could be given at the same time — would also help ease that burden of vaccinations in rural communities in low-income countries.

To expand these benefits outside of high-income countries, researchers need to figure out how to deal with the sensitive nature of mRNA, says Thaventhiran. Part of the challenge in rolling out COVID-19 vaccines has been keeping doses frozen to protect the mRNA from degradation.

Overall, the development of mRNA combination vaccines is evidence that mRNA has a positive future, says Weissman. “It’s not a coincidence.”