100 million doses of vaccine ready to ship within months

“these [candidate vaccine viruses] “It's like a seed stock that is saved in case a particular strain emerges.” Dr. David Diemertprofessor of medicine at George Washington University School of Medicine and Health Sciences and director of the GW Vaccine Research Unit.

If avian influenza begins to spread easily to people,[the candidate vaccine virus] “Using existing egg technology that we normally use for regular seasonal vaccines, we can send it to manufacturers to produce millions of doses of the vaccine,” he said.

a vaccine candidate virus It is a weakened, or attenuated, version of the virus. As a result, vaccinated people are less likely to develop an active infection.

This type of weakened virus can grow well in chicken eggs, and most manufacturers use it to make seasonal influenza vaccines.

Vaccine candidates also include a surface protein (known as hemagglutinin) from viruses that circulate in the community. This allows the vaccine to generate a protective immune response.

There are four H5N1 vaccine candidate viruses in the U.S. National Pre-Pandemic Influenza Vaccine Stockpile (NPIVS). Report STAT News. The avian influenza that affects dairy cows is H5N1.

Only two of these vaccine candidate viruses match the currently circulating avian influenza strains.

Studies show that vaccines based on these two vaccine candidate viruses “provide good cross-protection against circulating viruses in cattle,” said Demetre Daskalakis, director of the National Center for Immunization and Respiratory Diseases. I am. He spoke on the phone on May 1st..

but, Dr. Amesh AdaljaA senior researcher at the Johns Hopkins Center for Health Security at the Bloomberg School of Public Health warned that the vaccine candidate virus is not an “exact match” to the currently circulating H5N1 strain. This means that vaccines may not be very effective at preventing the disease.

In addition, the study Studies conducted in the mid-2000s found that the H5N1 vaccine did not cause a strong immune response in people unless given in sufficient doses. Or when given with compounds known as adjuvants that increase the immune response.

Adalja pointed out that the H5N1 vaccines we have in stockpile are not very good at eliciting an immune response.

“Even if it's a targeted virus,” Adalja said. “In clinical trials, the protective antibody levels that people had were moderate.”

one of them still exists H5N1 vaccine NPIVS is manufactured by CSL Seqirus, which supplies influenza vaccines to the U.S. market.

Still, Diemert believes that avian influenza vaccines based on NPIVS' two vaccine candidate viruses are effective and may be more effective than seasonal influenza vaccines.

This is because bird flu vaccines are likely to target only a single virus strain.

In contrast, multiple types of influenza can circulate during seasonal influenza season. seasonal influenza vaccine They are developed each year to target specific strains of influenza. Vaccines will be developed in the summer and early fall by looking at strains that are common in the Southern Hemisphere. However, the strains that become more common in North America during flu season may not be the ones targeted by vaccines.

As a result, seasonal influenza vaccines may ultimately target the following strains: influenza virus It was not distributed in that year.

“That's one of the reasons [seasonal flu vaccines] It's not a perfect match, so it's not 100% effective,” Diemert said.

Before an avian influenza vaccine can be rolled out, it must be approved by the Food and Drug Administration (FDA), which process To approve seasonal influenza vaccines, which are updated annually.

So this should go pretty smoothly, Diemert said. [bird flu] The vaccine will be manufactured using the same manufacturing process used every year. [for seasonal flu vaccines]”

“I'm also confident that if this particular strain were to emerge on a large scale, the FDA would accelerate things,” he said. “Therefore, we do not believe that regulatory approval will result in speed-limiting measures.”

In terms of getting the vaccine to those who need it most, “all the pieces are in place to be able to roll it out relatively quickly,” Diemert said.

However, when sending [the candidate vaccine virus] It will still take manufacturers weeks to months to produce all the doses needed,” he said.

This is especially difficult in a “rapidly changing situation” like the pandemic, he said. Dr. Peter Chin-Hongan infectious disease physician at UCSF Health.

Federal health officials estimate that: Over 100 million doses It can be shipped within 3-4 months. However, only 50 million people will be eligible, as it is expected that two doses will be required.

Vaccine production can also be affected by the same viruses that vaccines are designed to protect against.

Manufacturers often use chicken eggs to make influenza vaccines, but chickens are also susceptible to the avian influenza virus that affects cows.

Therefore, “global [influenza] There is a pandemic, birds are also dying, and supplies such as chicken eggs may be limited,” Adalja said.

As of May 6th, Over 5 million Chickens and other commercial or backyard poultry in the United States are affected by highly pathogenic viruses. Avian influenza (HPAI). The U.S. Department of Agriculture reports that this includes H5N1.

The big question is whether enough vaccines will be administered in time to make a difference.

“In the 2009 H1N1 pandemic, the pandemic was already over by the time a vaccine arrived,” Chin-Hong said.

During that trend, tens of millions of Americans Although they were vaccinated, the fall wave had subsided by the time vaccine doses were available.

But “now it's 2024, and things are changing,” Chin-Hong said, referring to the rapid development and rollout of COVID-19 vaccines. “If people put their mind to it, it could happen quickly…but the devil is in the details.”

Overall, “it's going to take some time to actually be ready to vaccinate everyone who is at risk for the flu,” Adalja said. “And, as I said, the vaccine candidate viruses that are stockpiled are not perfect matches. Even if it were a perfect match, [the H5N1 vaccine] It's not a good vaccine to begin with. ”

Federal health officials said the government also mRNA avian influenza vaccineis based on the same technology as Pfizer and Moderna's COVID-19 vaccines.

Chin-Hong said this type of vaccine could be updated more quickly to match the currently circulating virus strains. But he said these vaccines have their own challenges, including the need to store them at extremely cold temperatures.

Additionally, given that these vaccines are a new use of mRNA vaccine technology, the FDA may require clinical trials, which could delay their rollout to more people.

Other options for dealing with bird flu outbreaks in humans include antiviral drugs such as Tamiflu, which are given to people who are already infected.

“Different interventions speak to different people,” Chin-Hong said. “Americans generally prefer to treat something rather than prevent it, but that can be difficult.”

As we've seen with the COVID-19 pandemic, it's not just about how many doses of vaccine can be shipped, it's also about how many people can be vaccinated.

“The problem we have is that vaccine hesitancy is increasing right now and people may not be as motivated to get vaccinated,” Diemert said. “I don’t know if it’s any different. [hen egg] Influenza vaccine technology has been around for decades, and there's plenty of evidence that it's safe. ”

Chin-Hong said the current low rate of coronavirus vaccination among U.S. adults is a sign of vaccine fatigue.

About 22% of all U.S. adults have received an up-to-date coronavirus vaccine, and the rate is slightly better among older adults (38%). According to the CDC. Both rates are much lower than health officials expect.

“It shows how tired people are [with vaccination campaigns]” said Chinhong. “this [hesitancy] You'll need to approach it in the same way as making a detailed plan. [for rolling out the vaccines]”

Adalja is concerned not only about vaccine hesitancy, but also about growing public opposition to vaccines in general.

“For H1N1 in 2009, vaccination rates were below average because concerns raised by the anti-vaccination community (which were unwarranted concerns) deterred people from getting vaccinated,” he said. Stated.

However, he added, “Since COVID-19, the anti-vaccine movement is stronger than it has been in decades.” “So I think we will start the vaccination campaign. [future] It would be very difficult to deal with an emergency in the current political environment. ”

There is no indication that the H5N1 avian influenza circulating in dairy herds has developed the ability to spread easily to people. But federal health officials plan to roll out bird flu vaccines as a precaution.

The federal government has two vaccine candidate viruses in stockpile. They are weakened so they cannot infect humans or cause disease, but they grow well in chicken eggs, which is why influenza vaccines are most commonly made.

Health officials say the vaccine candidate virus is not “perfectly matched” to the current avian influenza virus, but should provide sufficient protection. But experts worry that vaccine fatigue could hinder inoculations.