Two possible bird flu vaccines could be available within weeks if needed

The U.S. has two vaccines ready in case the strain of bird flu circulating in dairy cows starts spreading easily to people, federal health officials said Wednesday. They could begin distributing doses widely within weeks if necessary.

So far, there is no evidence that H5N1 is spreading from person to person, although a dairy worker in Texas who worked closely with infected cattle had a mild infection and developed conjunctivitis, or conjunctivitis, in April.

At a news conference on Wednesday, government health officials said they are preparing for a potential scenario of animal-to-person — or person-to-person — transmission of H5N1. The virus took off in dairy cows, infecting at least 36 herds in nine statesraising concerns that it could acquire mutations that would facilitate transmission to humans.

Studies “suggest that the vaccines will offer good cross-protection against viruses from outbreaks in cattle,” said Demetre Daskalakis, director of the National Center for Immunization and Respiratory Diseases, on the call Wednesday.

Both vaccine candidates are already in the country’s reserves in limited quantities, officials said in a previous interview.

The Centers for Disease Control and Prevention also said Wednesday that it is testing blood samples from people previously vaccinated with an influenza vaccine to see if it generates an immune response, although it did not say which vaccine.

Dawn O’Connell, assistant secretary for preparedness and response at the Department of Health and Human Services, told NBC News previously that there are hundreds of thousands of prefilled syringes and vials ready to ship if needed.

“We have invested in a library of antigens to get them out as quickly as possible if we start to see a highly transmissible flu strain circulating,” O’Connell said.

H5N1 does not transmit easily between people, although global health authorities remain concerned due to its high mortality rate, which is around 50%, according to the World Health Organization.

There are no signs that the virus is mutating to be more transmissible between people, officials said Wednesday.

Vivien Dugan, who directs the CDC’s influenza division, said the government would begin considering vaccination if there were changes to the virus’s genetic code that affected existing countermeasures. It currently has a number of antiviral medications that target influenza viruses, including Tamiflu.

The people who need vaccination — and the number of doses the U.S. would need — would depend on how the virus changes and the extent of the outbreak, experts say.

Right now, there are more than 100 people, most of whom work with farmed animals, being monitored for signs of infection, authorities said.

Preparation in progress

If the U.S. needs the vaccines, the federal government could ship “hundreds of thousands of doses” within a few weeks, O’Connell said.

It could have more than 100 million doses shipped within three to four months.

Health officials expect people to need two doses of this vaccine, O’Connell added, meaning 100 million doses are only enough for 50 million people.

Again, given that this is a hypothesis, it is possible that the US does not need as many vaccines. But it could also produce more if necessary, O’Connell said.

They are produced using traditional vaccine technology that has been the standard approach to vaccines for decades. However, the process can take months.

O’Connell said the US is also pursuing a third vaccine based on the same mRNA technology used in Pfizer and Moderna’s Covid vaccines. She added that an mRNA vaccine could be faster to manufacture because “you can turn genetic sequencing on and off very easily.”

All three vaccines would also need approval from the Food and Drug Administration before they can be distributed in the US.

In a statement, the FDA said it is “actively engaged” with other federal health agencies in evaluating vaccine candidates against pandemic flu, should the need for a vaccine arise.

A series of unknowns

William Schaffner, an infectious disease expert at Vanderbilt University Medical Center, said having vaccine candidates on hand is important because it reduces the time it takes to get vaccines into people’s arms.

During the 2009 H1N1 swine flu pandemic, researchers eventually developed a vaccine to prevent the spread of the virus, but by the time the vaccines were manufactured and ready to be distributed, the outbreak had already disappeared, he said.

“It’s great that we have reduced the time needed to create a vaccine because we already have candidates available if they are needed,” he said.

Even though the government has two vaccine candidates, there are still a number of questions, including how much protection the vaccines would provide against infection and serious illness, said Dr. Judith O’Donnell, director of infection prevention and control at Penn Presbyterian Medical Center in Philadelphia.

“There’s a lot we don’t know about these vaccine candidates and how they will work,” she said.

The US has contracts with three pandemic flu vaccine manufacturers: GlaxoSmithKline, CSL Seqirus and Sanofi. One of the candidate vaccines is from CSL Sequirus.

A spokesperson for CSL Seqirus said the company does not have data available on the vaccine’s effectiveness because the number of human cases of H5N1 is too low for studies.

However, a phase 2 study testing a vaccine that targets a virus closely related to H5N1 shows that it generates a promising immune response and is expected to “cross-react with H5N1 viruses currently circulating in cattle in the US.” , said the spokesperson.

O’Connell said the government has a number of potential adjuvants, substances added to vaccines to boost the immune response, that could be used if necessary.

During the pandemic, the virus was typically severe in older adults and people with underlying health conditions. However, the 2009 H1N1 swine flu virus disproportionately affected young people. It is unclear how this strain of H5N1 would affect people because human infections are rare.

O’Donnell said that given the amount of vaccine skepticism, as well as vaccine fatigue due to the pandemic, the government would probably also need to start a vaccine campaign to persuade people to get vaccinated.

“It’s very disheartening to see so much vaccine skepticism and fatigue,” she said.