We love mRNA. Let’s use it for the flu shot too

The past year has been a story of triumph in the vaccine world, with the rapid development of two very successful vaccines for Covid-19, one developed by Modern and the other by Pfizer and BioNTech. Now that flu season is approaching, why are we still using 50-year-old technology for the flu vaccine?

The reason the Covid-19 vaccines were developed so quickly is that they used a new type of vaccine technology, much faster and easier to create, based on messenger RNA, or mRNA. What’s even more exciting is that we now have an overwhelming amount of evidence, drawn from real-world experience, that these vaccines are remarkably safe and effective.

Now anti-vaccines and “vaccine-hesitant” claim they don’t trust the vaccine because it was developed too quickly. This is ridiculous: The real reason they don’t trust the vaccine is because they consume a regular regimen of anti-vaccine nonsense, promoted by a combination of right-wing media and the dozen disinformation (which include fanatics on the left as well as on the right). But let’s not go down that rabbit hole today.

So what is an mRNA vaccine? Here’s a brief explanation, and then we’ll look at the flu shot. (Note: Please feel free to go ahead if you already understand the technology.)

Messenger RNA vaccines have been in development for decades, long before the onset of Covid-19. The technology has required a series of breakthroughs over the years, as described in a recent Nature new stories, and many scientists have contributed to it. It was not used in vaccines partly because it was not ready, but also because we rely on private companies to develop vaccines, and few of them were interested in investing in a new one. technology not yet approved. But I digress.

Messenger RNA is the substance all of your cells use to translate your genes, which are encoded in DNA, into proteins. The basic process is that the DNA of a gene is copied into pieces of mRNA, where the letters of DNA, ACGT, are replaced with slightly different (chemically) RNA letters, ACGU.

Every cell in your body is full of mRNA, all the time. This is the essence of life, so of course it’s totally safe. Each cell uses mRNA to make proteins, which do most of the actual work that keeps you alive.

Here’s what’s great about mRNA vaccines: All they do is introduce mRNA into your cells that codes for a single protein of the virus, which is called “Spike” in the case of Covid vaccines. -19.

Your own cells then make the Spike protein, but they don’t make much! They only make a few copies because mRNA doesn’t last very long. And because there is no DNA copy of the Spike protein in your genome, once the vaccine mRNA breaks down, it is gone forever.

The other brilliant thing is that your own immune system recognizes Spike as a foreign protein, and it generates cells that will recognize any future infections where the Spike protein is present. If you are subsequently infected with SARS-CoV-2 (the Covid-19 virus), your immune system is primed and ready, and in the vast majority of cases, it attacks and destroys the virus before you get sick. .

So that’s it: an mRNA vaccine is simply a small bundle made of fat molecules (called liposomes) which contains a few copies of mRNA encoding a viral protein. Nothing prevents us now from creating similar vaccines against influenza or against other viruses for which we need new vaccines. (In the case of the flu, we can use mRNA from a gene called hemagglutinin, but again, I digress.)

We make new flu vaccines every year because the flu is constantly changing. In most years, the influenza vaccine is not very suitable for circulating strains of the virus, and therefore the vaccine is not very effective. In a good year it can be 60-70% effective, but in bad years it can be much worse. Much of the problem is with the way we create the vaccine.

In the United States, we make most of our flu shots by growing flu viruses in chicken eggs. (No, I’m not making this up.) Around February of each year, a panel of experts selects 4 strains of the virus that they believe will most likely correspond to viruses for the following flu season, which usually intensifies in November. or December. (Here are the picks for this year.)

Once the experts have selected the vaccine strains, the manufacturing process begins, first by checking whether the 4 strains will grow robustly in chicken eggs. If they don’t, the panel may need to switch to different strains that are less likely to work. No, I’m not kidding: The success of the flu vaccine depends on its growth in eggs. This is one of the reasons why, in some years, the flu shot is a failure. That would just never happen if we used mRNA technology.

With mRNA vaccines, we don’t need to grow viruses at all. The mRNA for a single gene – hemagglutinin for influenza – can simply be synthesized in large quantities, just as we are currently doing for the Spike protein in SARS-CoV-2. Or for an even more effective vaccine, we could add the gene for neuraminidase, the other influenza protein that our immune system can “see”.

An influenza mRNA vaccine would be much cheaper to manufacture, not requiring huge chicken farms. (This year, 82% of influenza doses in the United States were made this way.) Even more important, however, is that an mRNA influenza vaccine would likely be much more effective at controlling the severity of the infection itself.

Why aren’t we doing it already? Simply put, it’s because we rely on private companies to take the initiative, and it’s not worth it for them to test and validate an entirely new vaccine, which requires a substantial investment. There is also a simple solution, the same as the one we used for Covid-19: the government should take the lead.

We are now at the start of flu season, which almost disappeared last year through our social distancing and masking behavior. I have had the flu shot and millions more are given around the world. As recently as last week, a first report from Europe indicated that flu season this year could be “severe”, which is the last thing we need with Covid-19 still raging.

We don’t yet know whether this year’s flu shot will work or not, but there’s a good chance that, based on past performance, it won’t be great. (It’s always better than nothing, I should add.) If we want a better flu vaccine, now is the time to start developing a new one using mRNA. If private industry does not step in, one of the dozens of countries has the expertise to do so.