There could be a combined COVID-19 and flu shot in our future, although it won’t be ready for this year’s flu season.On Monday, vaccine maker Moderna announced positive late-stage trial results for its COVID-flu combination vaccine it calls mRNA-1083.Calling the outcome of the late-stage trial “breakthrough results,” Moderna’s Chief Medical Affairs Officer Francesca Ceddia told CNN that people in the trial who got mRNA-1083 showed an improved immune response compared with those who got the standalone flu and COVID vaccines that are available now. The results were true even for people in the trial who were 65 years and older. Generally, older people don’t mount as robust a response to vaccines as younger people do.“When we think about the combination vaccine, we often only think about the element of convenience, one shot instead of two, but what is really, really breakthrough is the fact that you not only offer that advantage, you also offer the proof of clinical benefit. I think this is the most important message,” Ceddia said.Other companies have been testing a combined COVID-flu vaccine, but Moderna is the first to announce positive late-stage trial results.Public health leaders say the world could use more ways to protect people from both viruses. Millions of people get sick with the flu and now COVID every year. For the last flu season, the Centers for Disease Control and Prevention estimates 35 to 64 million people got sick with the flu in the United States. Between 390,000 and 810,000 people were so sick they were hospitalized and up to 71,000 people died. Just for last fall and winter, COVID sent more than a half-million people in the U.S. to the hospital and killed 40,000, according to data presented last week to the Food and Drug Administration’s independent vaccine advisers, who were discussing how to update COVID vaccines for the fall.Moderna’s Phase 3 trial was a randomized, observer-blind, active control study, meaning that even the clinicians giving the shots didn’t know who got which vaccines. The trial studied the vaccine in two different age groups with about 4,000 adults in each age category.For one part of the study, Moderna compared the immune reaction of adults 65 and older who got mRNA-1083 and another group with the same age range who got a co-administered COVID-19 vaccine, Moderna’s Spikevax, and an enhanced flu vaccine, Fluzone HD. Doctors recommend seniors get more powerful flu vaccines due to their inhibited immune systems.For the other part of the trial, researchers compared how slightly younger adults, ages 50 to 64, did when they got the mRNA-1083 vaccine to another group within the same age range who got Spikevax and a standard dose flu vaccine called Fluarix.Study results showed that in both age groups, the experimental combination vaccine elicited a statistically significant higher immune response against three strains of the flu and against COVID-19, compared with the co-administered shots.“The titers are significantly higher,” Ceddia said. “This is better actually.” A titer is a lab test that measures the number of antibodies in the blood and it can be used to prove how immune someone is to the disease.In terms of safety, the combined vaccine was well-tolerated, Moderna said, and the adverse reactions were similar to what people experienced with the co-administered vaccines. The most common complaints were pain at the injection site, tiredness, muscle pain and headaches.The study isn’t peer-reviewed yet, but Moderna said it plans to present data from this late-stage trial at an upcoming medical conference and it will also submit the trial for publication. Moderna also said it will talk to the FDA about possible next steps.“We need to engage with regulators but our aspiration is to have it approved for fall 2025,” Moderna CEO Stéphane Bancel told CNN.Sue Peschin, the president and CEO of the Alliance for Aging Research, a nonprofit dedicated to improving aging and health that encourages more equitable access to vaccines, said a combined shot could be a significant help to public health.In addition to intensifying vaccine hesitancy in the U.S., people have developed a kind of vaccine fatigue after the pandemic, Peschin said. Peschin pointed to the drop in the uptake in standard vaccines such as the MMR vaccine, as well as in seasonal vaccines.Few people got the latest COVID shot, studies show. Only about 25% of the eligible population has received the latest COVID-19 vaccine, according to a presentation to the FDA last week. Many more adults got the flu shot with nearly half of the adult population getting one last season, according to the CDC, a number that was slightly higher than the year before.“We want to see that go up and if there’s a way to do that by combining the vaccines, then that’s better for everyone because it helps protect everyone in the community,” Peschin said. “We would love to see the combination vaccines come to market if the FDA deems them safe and effective.”CNN’s Meg Tirrell contributed to this report.