A new flu vaccine might not seem like a big deal, but this isn’t the kind of vaccine you can currently get at the local pharmacy. In a study published this week in Science, researchers from the University of Pennsylvania reported the first results from animal trials of a new messenger RNA-based vaccine against the flu. This is not a vaccine against a specific strain of flu, like those which are mixed together to generate the cocktail seen in annual flu shots. This is a vaccine against flu. All flu. Even against strains we’ve yet to see.
The reason that flu is so difficult to stop, and that it returns year after year in spite of readily available vaccines, is that flu viruses have a revolving set of surface proteins that can be swapped out without affecting the virus’ effectiveness, while allowing the virus to bypass existing immunity. So people can catch Influenza Type A H3N2 in one season, the follow it up with H5N1 the next year. Or they can come down with a version of the equally severe Influenza Type B with wholly different mix.
The Type A flu is particularly worrisome, because it can spread from animals to people. Many of the past large pandemics have emerged in just this way, with a new flu strain jumping from birds or farm animals to people. But if the new vaccine is as effective as animal trials suggest, the possibility of such a pandemic would be greatly reduced. Because this is a vaccine against Type A or Type B, H-anything N-anything. It’s a universal flu vaccine.
In those names of flu, “H” stands for hemagglutinin, and it’s the protein the virus uses to stick to the outside of a cell. “N” is kind of the opposite. It’s the protein neuraminidase that the virus uses to escape from a cell after reproducing. If you think of human cells as having lots of entry and exit doors, each one of which has a different lock, H and N are the keys the virus is carrying to get in and get out.
If two viruses that are are coded H5N1 and H5N3, they’re both carrying the same (or similar) version of hemagglutinin, but they’re carrying quite different versions of neuraminidase. Still, if someone was recently infected by the first virus, they’d have pretty good protection against the second. However, if something like H3N2 rolled up, neither of the defenses the body has cranked up against H5N1 would hold.
Each year, researchers look at the cases of flu they are seeing, with an eye toward those which haven’t been around in awhile, and try to produce a vaccine that hits the most likely varieties. They get especially worried when they see a virus in animals carrying a protein pair that hasn’t run around in humans for decades.
That’s what makes this new vaccine strategy exciting.
If it seems like that vaccine design includes just about every buzzword for hot new vaccine technologies, you’re right. The mRNA COVID-19 vaccines from BioNTech and Moderna are the fist such to be authorized for use in humans. But now that the door is open, there’s tremendous potential in this technology, including a superior flu vaccine.
The vaccine produced by by the Penn team targets all 18 known versions of hemagglutinin. So even if something like the current flu being passed around among bird species makes the leap to humans tomorrow, we would already have a vaccine that was substantially effective.
This wouldn’t mean an end to annual flu shots, and those shots would continue to focus on the most likely varieties to be seen in a season. However, they could also sharply reduce the chance of serious illness from any flu.
There are still several steps remaining to show that this vaccine is safe and effective for humans. Among other things, there are concerns that getting enough vaccine to generate a response to all 18 versions of “H” may turn out to require too large a dose, leading to unpleasant reactions. (Which is exactly why it’s difficult to make a universal COVID-19 shot that addresses all known variants.)
But since the technologies involved in this vaccine have already been tested against COVID-19, expect this vaccine to move forward without running into worries about the use of mRNA or lipid capsules. It won’t be a part of any vaccine you use this year. But next year? Maybe.
The reason that flu is so difficult to stop, and that it returns year after year in spite of readily available vaccines, is that flu viruses have a revolving set of surface proteins that can be swapped out without affecting the virus’ effectiveness, while allowing the virus to bypass existing immunity. So people can catch Influenza Type A H3N2 in one season, the follow it up with H5N1 the next year. Or they can come down with a version of the equally severe Influenza Type B with wholly different mix.
The Type A flu is particularly worrisome, because it can spread from animals to people. Many of the past large pandemics have emerged in just this way, with a new flu strain jumping from birds or farm animals to people. But if the new vaccine is as effective as animal trials suggest, the possibility of such a pandemic would be greatly reduced. Because this is a vaccine against Type A or Type B, H-anything N-anything. It’s a universal flu vaccine.
In those names of flu, “H” stands for hemagglutinin, and it’s the protein the virus uses to stick to the outside of a cell. “N” is kind of the opposite. It’s the protein neuraminidase that the virus uses to escape from a cell after reproducing. If you think of human cells as having lots of entry and exit doors, each one of which has a different lock, H and N are the keys the virus is carrying to get in and get out.
If two viruses that are are coded H5N1 and H5N3, they’re both carrying the same (or similar) version of hemagglutinin, but they’re carrying quite different versions of neuraminidase. Still, if someone was recently infected by the first virus, they’d have pretty good protection against the second. However, if something like H3N2 rolled up, neither of the defenses the body has cranked up against H5N1 would hold.
Each year, researchers look at the cases of flu they are seeing, with an eye toward those which haven’t been around in awhile, and try to produce a vaccine that hits the most likely varieties. They get especially worried when they see a virus in animals carrying a protein pair that hasn’t run around in humans for decades.
That’s what makes this new vaccine strategy exciting.
If it seems like that vaccine design includes just about every buzzword for hot new vaccine technologies, you’re right. The mRNA COVID-19 vaccines from BioNTech and Moderna are the fist such to be authorized for use in humans. But now that the door is open, there’s tremendous potential in this technology, including a superior flu vaccine.
The vaccine produced by by the Penn team targets all 18 known versions of hemagglutinin. So even if something like the current flu being passed around among bird species makes the leap to humans tomorrow, we would already have a vaccine that was substantially effective.
This wouldn’t mean an end to annual flu shots, and those shots would continue to focus on the most likely varieties to be seen in a season. However, they could also sharply reduce the chance of serious illness from any flu.
There are still several steps remaining to show that this vaccine is safe and effective for humans. Among other things, there are concerns that getting enough vaccine to generate a response to all 18 versions of “H” may turn out to require too large a dose, leading to unpleasant reactions. (Which is exactly why it’s difficult to make a universal COVID-19 shot that addresses all known variants.)
But since the technologies involved in this vaccine have already been tested against COVID-19, expect this vaccine to move forward without running into worries about the use of mRNA or lipid capsules. It won’t be a part of any vaccine you use this year. But next year? Maybe.