Ever since it first came on the scene, the SARS-CoV-2 virus has invited comparisons to the flu. You can see why: they’re both nasty, potentially fatal viruses that spread through the air and disproportionately kill the elderly and vulnerable in society. Of course, we now know that these superficial similarities hide some deadly differences: COVID-19 is far more virulent and dangerous than the flu. But as the science on vaccines continues to evolve, it’s starting to look like the two diseases might have something else in common too – in the form of an annual booster shot to help our bodies fight them.

Moderna, the biotech company behind one of the new mRNA vaccines, announced a slew of advances at their annual R&D Day last week, including the development of mRNA vaccines against cancer, heart disease, and various respiratory diseases. But one program they announced – the first steps towards a combination flu and COVID-19 booster shot – is particularly noteworthy, as health researchers and governments look to the future of COVID-19 vaccinations.

“Today we are announcing the first step in our novel respiratory vaccine program with the development of a single-dose vaccine that combines a booster against COVID-19 and a booster against flu,” Stéphane Bancel, Chief Executive Officer of Moderna, said in a statement. “We are making progress on enrolling patients in our rare disease programs, and we are fully enrolled in our personalized cancer vaccine trial. We believe this is just the beginning of a new age of information-based medicines.”

The vaccine programs that have rolled out across much of the world so far have been an extraordinary success, saving hundreds of thousands of lives in the US alone. They’re safe and effective, and if it wasn’t for a strain known as the Delta variant, our only problem by now might have been trying to stop people poisoning themselves with horse medicine. But the Delta variant is a challenge: it’s more transmissible, potentially more dangerous, and, crucially, more able to overcome our vaccines. That’s not to say the vaccines are useless – they still offer up to 80 percent effectiveness against the Delta variant – but do offer less protection than they did against the original virus, and at least one (not yet peer-reviewed) study has found a noticeable decrease in effectiveness over the three months following vaccination.

So what do we do when a vaccine wears off? We get a booster shot – and that’s exactly what governments like the UK and US have been considering rolling out. But while the UK’s booster program is apparently ready to go for the over-50s and those with underlying health issues, in the US things are looking a bit more chaotic. While the White House originally announced the booster shot roll-out would begin by September 20, many scientists including some from the FDA and CDC argue that they’re not necessary – or at least, that the evidence does not yet suggest that they are necessary.

“Science takes time,” one CDC official told Politico. “I don’t know how many times we have to say this… The CDC is getting out what it can when it can.”

But if booster shots do end up being necessary, the Moderna combined vaccine may end up being part of our everyday life. In the UK, vaccines minister Nadhim Zahawi has already proposed delivering annual COVID-19 booster shots at the same time as flu shots, and a combined dose would likely be an inviting option.

“I am proud of the progress that the Moderna team has made in advancing our best-in-class mRNA pipeline while addressing the global COVID-19 pandemic,” said Bancel. “We believe our mRNA platform can solve the world’s greatest health challenges.”