Pharmaceutical company Moderna has announced that a combination vaccine it has been developing against flu and COVID-19 has performed well so far in Phase 3 trials. The data are yet to be submitted for publication in a peer-reviewed journal, but the company says their combi vaccine has produced stronger immune responses than the already-licensed vaccines it was compared to.

Moderna became a household name thanks to the success of its mRNA vaccine against COVID-19. Along with the Pfizer/BioNTech mRNA vaccine, it remains a cornerstone of the public health response to the pandemic, with the architects of the technology behind them winning a Nobel Prize.

While other vaccines played their part in gaining control of the spread of COVID, some – like the AstraZeneca vaccine – are now being withdrawn, while the mRNA vaccines continue to be updated to match the latest variants.

But COVID-19 is not the only threat out there, and a number of research projects are currently looking to apply mRNA vaccines to other diseases, including cancer. When it comes to respiratory pathogens, a clear target would be influenza. There are around a billion cases of seasonal flu annually and hundreds of thousands of deaths, not to mention the ever-present Damocles’ sword of a possible future pandemic.

Influenza viruses and SARS-CoV-2 (the virus behind COVID-19) share a tendency to mutate rapidly. That’s why regular booster shots are recommended for COVID and why the seasonal flu shot is updated every year. Moderna’s combi vaccine seeks to put both shots into one handy package.

“Combination vaccines have the potential to reduce the burden of respiratory viruses on health systems and pharmacies, as well as offer people more convenient vaccination options that could improve compliance and provide stronger protection from seasonal illnesses,” said CEO Stéphane Bancel in a statement.

The combi vaccine, called mRNA-1083, incorporates a candidate vaccine for seasonal flu (mRNA-1010) and Moderna’s latest COVID-19 vaccine (mRNA-1283). The Phase 3 clinical trial, which is still ongoing, has recruited two cohorts of approximately 4,000 adults each.

The first cohort are all aged 65 and over. Participants have been randomly assigned to receive either mRNA-1083, or a combination of Moderna’s current COVID vaccine (Spikevax^®) and a licensed flu vaccine called Fluzone HD^®.

The second cohort are aged between 50 and 64. In this group, participants have either received mRNA-1083 or a combination of Spikevax and a standard flu vaccine (Fluarix^®).

Moderna reports that the immune response elicited by mRNA-1083 was stronger than that produced by the separate vaccines against SARS-CoV-2 and three different flu strains: H1N1, H3N2, and B/Victoria. mRNA-1083 was also found to be safe, and the majority of side effects experienced were mild and similar to those caused by the separate vaccines. The most common side effects were pain at the injection site, fatigue, muscle aches, and headache.

Moderna now plans to present the data at a medical conference and hopes to publish the findings in a peer-reviewed journal.

“Moderna is the only company with a positive Phase 3 flu and COVID combination vaccine,” said Bancel. “Building on the momentum of positive Phase 3 data across our respiratory portfolio, we continue to address significant unmet medical needs and advance public health.”