We may get a universal flu vaccine, thanks to mRNA technology

The mRNA vaccines for Covid-19 are an amazing story: a new vaccine developed in a matter of weeks for a brand-new virus, SARS-CoV-2, at the beginning of the pandemic in early 2020. Clinical trials moved forward at record speed, and by December of that year we had an approved vaccine that was safe and over 90% effective against Covid-19.

Why not use this mRNA technology for other vaccines, especially for the flu? When I asked this question last year, I didn’t realize that a group of scientists at the University of Pennsylvania were already hard at work making this idea a reality. They’ve just published their first results, and the news is very encouraging.

But first, some background. Messenger RNA (mRNA) vaccine technology was the big breakthrough behind the Covid-19 vaccines. Invented by Katalin Karikó and Drew Weissman at the University of Pennsylvania, the idea is, at its core, very simple: take the genetic code for a protein from the virus (any protein can be used, and for Covid-19 this protein is called Spike), and inject it into someone’s arm. (The genetic code I’m referring to here is the mRNA that encodes the protein.) From there, the cells of the human host manufacture the protein–not too much, though, because mRNA quickly degrades once it’s in your body.

What’s kind of amazing is that the human immune system will then recognize the Spike protein as an invader, and generate antibodies against it. From that point on, the person who received the vaccine will be prepared to fight off a real infection by Covid-19. In other words, they’ll be immunized.

The actual development of this technology was much more complicated than I’m describing here. First, you can’t just inject mRNA without causing a lot of inflammation, which can be dangerous. Weissman and Karikó solved that problem by using chemically modified mRNA. Second, you need to package the mRNA in something; the scientists discovered that they could use little packages of fat molecules called liposomes to make an effective container. Eventually, they got it to work, and the rest is (recent) history. Both the Moderna and Pfizer/BioNTech vaccines use mRNA technology.

Now about this new “universal” flu vaccine, and why it’s so much better than what we currently use. The annual flu shot contains pieces of one protein from 4 different influenza strains. Each year, as the flu itself evolves, the 4 strains used in the flu vaccine are fine-tuned in an effort to keep up. In some years, this effort fails and the vaccine just doesn’t work very well, for reasons I explained here.

One huge problem is that the current flu vaccine process grows the flu virus in chicken eggs, and sometimes the darned thing just won’t grow! So in those years, the vaccine manufacturers must switch to another flu strain, one not as well-matched to what’s circulating. The result is a vaccine that sort of sucks, although it’s usually better than nothing.

With mRNA, you don’t have to grow anything in chicken eggs, and you aren’t limited to just 4 strains. As the new research shows, you can put ALL 20 known influenza strains in the same vaccine, and it protects subjects against all of them. It even protects against other flu strains that weren’t in the vaccine. To create the vaccine, scientists simply synthesized the mRNA that encodes the surface protein of the flu, hemagglutinin, from 20 different flu strains. The synthesis process is already being done on an industrial scale for the Covid-19 vaccines, and the same process will work for any mRNA, from any virus.

In the new research, scientists at UPenn led by Scott Hensley and Drew Weissman (the co-inventor of the mRNA vaccine) inserted all 20 flu strains in a single vaccine. They found “that the vaccine dramatically reduced signs of illness and protected from death, even when the animals were exposed to flu strains different from those used in making the vaccine.”

Did I mention that the subjects in the new study were mice and ferrets, not people? Well, this experiment is just the beginning: we’ll need further trials to test the safety and efficacy of this vaccine in people. Those are much, much more costly, though, and it’s not clear when or even if those trials will happen.

If we had a universal flu vaccine, we might no longer need the annual flu shots that we beg everyone to get each year. So when can we expect to see this new 20-strain vaccine?

Well, there’s the rub. Even if this new flu vaccine works perfectly in human testing, we might never get it. At the moment, we are completely dependent on private companies to develop vaccines. At the beginning of the Covid-19 pandemic, the U.S. created incentives for vaccine manufacturers by promising to buy millions of doses, and–fortunately–that worked. We’ve never tried anything like that with the flu vaccine.

We need to re-think our dependence on private, for-profit companies for this critically important public health technology. Perhaps it’s time for the government to step in and make sure we get this vaccine, whether through incentives like the ones used to create the Covid-19 vaccine, or through a direct effort by the government itself (as other countries have done) to create a universal flu vaccine. A universal flu vaccine will save tens of thousands of lives every year. Let’s hope we get there.