While the combined vaccine won't be available for this year's flu season, the breakthrough results are promising for future immunization efforts.

Moderna's Chief Medical Affairs Officer, Francesca Ceddia, described the outcome of the trial as "breakthrough results." Participants who received mRNA-1083 showed an improved immune response, even compared to those who received separate flu and Covid vaccines currently available in the market. This increased immune response was observed across all age groups, including individuals aged 65 and older, who typically exhibit a weaker response to vaccines.

Ceddia emphasized that the convenience of a one-shot combination vaccine is not the only advantage. The mRNA-1083 vaccine also offers proof of clinical benefit, which is crucial in protecting individuals from both viruses.

While other companies have been testing combined Covid-flu vaccines, Moderna is the first to announce positive late-stage trial results. Public health leaders believe that such vaccines are essential, as millions of people fall ill to both the flu and Covid each year.

During the previous flu season, the United States Centers for Disease Control and Prevention estimated that 35 to 64 million Americans contracted the flu, resulting in hospitalizations ranging from 390,000 to 810,000 and up to 71,000 deaths. Similarly, Covid-19 sent over half a million Americans to the hospital and caused 40,000 deaths during the recent fall and winter period.

Moderna's Phase 3 trial involved a randomized, observer-blind, active control study, ensuring that even the clinicians administering the shots remained unaware of which vaccines the participants received. The trial examined approximately 4,000 adults in two different age groups.

The immune response of adults aged 65 and older who received mRNA-1083 was compared to those who received a combination of Moderna's Spikevax Covid-19 vaccine and an enhanced flu vaccine called Fluzone HD. Furthermore, the trial compared the response of younger adults aged 50 to 64 who received mRNA-1083 with those who received Spikevax along with a standard flu vaccine known as Fluarix.

The study's results indicated that the experimental combination vaccine elicited a significantly higher immune response against three strains of the flu and Covid-19, compared to the co-administered shots. This heightened immune response was measured through lab tests that assessed the number of antibodies in the blood, known as titers.

Moderna reported that the combined vaccine was well-tolerated, with adverse reactions similar to those associated with the administration of the individual vaccines. The most common complaints included pain at the injection site, tiredness, muscle pain, and headaches.

While the study results have not yet undergone peer review, Moderna plans to present the data at an upcoming medical conference and submit the trial for publication. The company also intends to engage with regulators, including the US Food and Drug Administration (FDA), to discuss potential next steps.

Moderna CEO Stéphane Bancel stated that the company's aspiration is to have the combined vaccine approved for fall 2025. Public health advocates, such as Sue Peschin, president and CEO of the Alliance for Aging Research, applaud the potential of a combined shot, as it could help address vaccine hesitancy and vaccine fatigue among the public.

Currently, only about 25% of the eligible population has received the latest Covid-19 vaccine, while nearly half of the US adult population received the flu shot last season. Combining vaccines could potentially increase vaccination rates and offer better protection for the community. However, the FDA will ultimately decide on the safety and effectiveness of combination vaccines before they can be made available to the public.