A Bird Flu Vaccine Might Come Too Late to Save Us from H5N1NEWS | 06 November 2024Color-enhanced transmission electron microscope image of avian influenza (bird flu). Highly pathogenic avian influenza variants such as H5N1 and H7N9 have been transmitted to humans. New variants of avian influenza viruses are emerging as a result of hosts carrying multiple viral variants that leads to the mixing of the viral genomes.
H5N1 bird flu is here. It’s moving from animals to people in ways not seen before. It’s spreading to new species and new places, and this spread is largely happening under the radar.
So far 36 human cases have been reported in six U.S. states: California, Colorado, Michigan, Missouri, Texas and Washington. Those are just the cases that health officials know about. Not all states are testing people or animals. The tests for the virus are flawed and in short supply.
Most health officials say they are not really worried about H5N1 influenza just yet because the virus is so very rarely infecting people compared to the number of cattle and birds it’s affected. When it does, so far, it usually causes very mild symptoms and there’s no evidence so far that it can be transmitted from person to person. That’s the scary scenario: a new virus that causes severe disease among people that can be easily transmitted from one person to another. We are not there yet.
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Plus the U.S. government is stockpiling H5N1 vaccines. But don’t count on those vaccines saving us if this virus does what flu viruses sometimes do, and turns into a pandemic form. It won’t oblige humanity by slowly mutating, giving people a chance to ramp up vaccines quickly.
“It is going to happen fast,” says Ali Khan, dean of the University of Nebraska Medical Center College of Public Health and a veteran of numerous disease outbreaks, from influenza to Ebola.
The world just saw this happen. COVID appeared suddenly and spread globally before alarm bells rang. Even with the new, quick-turn technology of mRNA vaccines, it took just about a year after SARS-CoV-2 started its global spread to get the first doses into arms. By that point, 300,000 people had died in the U.S. and hundreds of thousands more—possibly millions—died around the world before vaccines were fully deployed.
We’ve somehow not learned this valuable lesson to prepare early for a bird flu pandemic, even though this particular influenza virus has been scaring doctors, scientists and public health experts for far longer. H5N1 is a well-known and well-characterized virus, and in theory there could be a large bank of vaccines ready to go should it acquire the ability to spread easily from person to person.
But there isn’t. The U.S. currently has fewer than five million vaccines matched to the H5N1 strain that is circulating among cattle and occasionally infecting people right now. The federal government has contracts out that will stock up a supply of 10 million filled syringes but not until spring of 2025. And because it will take two doses to protect, that’s enough to fully vaccinate just five million people. That’s less than 2 percent of the U.S. population—to say nothing of the rest of the world.
And, perhaps unbelievably after the COVID experience, the U.S. does not have a licensed mRNA vaccine against flu—one that could be quickly adapted to match a mutating strain. Instead, vaccines being stockpiled to protect against pandemic influenza strains are made using mostly nearly century-old egg-based technology. It’s an uncertain and slow method that would take months to ramp up in an emergency. “We think 100 million doses within five months based on current capabilities,” said Robert Johnson, director of the medical countermeasures program at Health and Human Services Department’s Administration for Strategic Preparedness and Response.
Those are the approved and licensed vaccines. Newer vaccines would have to finish testing and clear regulatory hurdles. There are currently no public plans for distributing or administering H5N1 pandemic vaccines, although that could change if person-to-person transmission occurs or if the virus becomes more virulent.
Vaccine maker Moderna—which marketed one of the first COVID vaccines using the new, nimble mRNA technology—says it has an H5 flu virus vaccine in phase 2 trials. It’s got a deal with the U.S. government. Pfizer, the other maker of mRNA vaccines, says it also has an H5 pandemic flu vaccine in the works but no U.S. government deal yet.
Scott Hensley, an immunologist at the University of Pennsylvania in Philadelphia, has been working on an mRNA vaccine to protect against flu that he hopes would be quick to produce and easy to adapt to match a new pandemic strain. But he and his colleagues had to stop that work to deal with COVID, and they’re only just getting back up to speed.
“If a pandemic happened tomorrow there is no doubt that we would see conventional egg-based vaccines being deployed as well as mRNA vaccines. So let’s hope a pandemic doesn’t happen tomorrow,” Hensley says.
The trouble with making influenza vaccines starts with the flu virus itself. It’s exceptionally prone to mutation or, worse, mixing with other viruses. This is why the flu vaccines usually change from one season to another and why flu vaccines don’t fully protect against infection.
The H5N1 virus now infecting cattle is different from the H5N1 viruses that first showed up in poultry in 1997 and the early 2000s and spread in Asia, Africa and the Middle East, by some estimates killing up to about 50 percent of people who were infected.
Thus it makes no sense to make 600 million doses of H5N1 vaccine just in case the virus now infecting cattle decides to start infecting and killing people. It might change again, or even disappear. “If this H5 causes a pandemic, it likely is not going to be identical to whatever is circulating in cows [currently],” Hensley says. It will have to adapt to infect people.
So government agencies and flu vaccine makers and researchers are walking a fine line, watching the virus and gambling that, if and when it changes, they will notice and can make the right vaccine quickly enough. “It’s simply not possible, because the virus continually evolves, to have a constant stockpile—a large stockpile—of vaccines,” Johnson said at an October 8 meeting of the Bipartisan Commission on Biodefense, a U.S. think tank.
There is a theoretical solution to this problem: a flu vaccine that protects against all strains of flu, helping the body’s immune system identify parts of the virus that are consistent from season to season and from strain to strain. “We need a moonshot project for a universal flu vaccine,” Khan says.
A universal vaccine would protect people against seasonal flu as well as against new pandemic strains, like the H1N1 strain that came from pigs in Mexico in 2009 to join the annual mix of circulating flu viruses.
Hensley’s team has something close in an mRNA vaccine that provides immunity against all 20 known influenza subtypes. But he’s the first to say this wouldn’t be a universal flu vaccine but rather a primer to give people an initial level of protection. “It wouldn’t replace seasonal vaccination. You are still stuck with this problem of making booster vaccines,” he says, because his lab’s shot only targets known subtypes. Nonetheless this type of vaccine could address the stockpile problem. Ongoing production would be less wasteful than a one-off effort.
Despite decades of work, no lab has been able to develop a vaccine that protects people against mutations that make flu subtypes drift from season to season. And there’s been little to no political push for one.
That’s in no small part a result of growing public hostility. When COVID broke out, people were largely open to vaccines. Then-president Donald Trump touted his government’s rollout of the vaccine, but he has since helped feed vaccine skepticism. Neither Trump nor his Democratic opponent for president, Vice President Kamala Harris, mentions pandemic preparedness in their respective campaign platforms.
Even uptake of routine childhood vaccines is falling. “The lack of trust around vaccines does put us in a very bad place. We do know that people are dying because they are not getting vaccinated against COVID,” Khan says. The U.S. Centers for Disease Control and Prevention reports that only 11 percent of adults and just 7 percent of pregnant women have received the latest COVID vaccine.
Some states have loosened vaccine requirements and recommendations, something that worries Khan and other public health experts. Vaccines cannot help anyone if people don’t get them. Politicians who don’t promote the need for pandemic preparations are gambling that the next one won’t hit during their terms in office. “This is all going to potentially come home to roost with the next pandemic,” Khan says.
This is an opinion and analysis article, and the views expressed by the author or authors are not necessarily those of Scientific American.Author: Maggie Fox. Source
