Most of the world's H1N1 vaccine started in 30 chicken eggs kept in a warren of labs at New York Medical College. Bucher and her team did what they always do: take an isolated H1N1 flu strain and allow it to exchange genetic parts with another flu known to grow well in chicken eggs with...
VALHALLA, N.Y. — Most of the world’s H1N1 vaccine started in 30 chicken eggs kept in a warren of labs at New York Medical College.
Working seven days a week, microbiologist Doris Bucher and her eight assistants made “seeds” that manufacturers are using to grow the vaccine used in the swine-flu shot.
“It was very intense,” Bucher said. “We all knew how important this was. The world was resting on our shoulders.”
Bucher and her team did what they always do: take an isolated H1N1 flu strain and allow it to exchange genetic parts with another flu known to grow well in chicken eggs with embryos. The new hybrid would be the vaccine seed.
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The seed, designated NYMC X-179, proved a robust grower in the lab. But it was a different story for some of the manufacturers charged with producing 250 million doses of H1N1 vaccine ordered by the U.S. government. They found that the vaccine didn’t grow as quickly as typical seasonal vaccine. The delays are being blamed not only on the slow-growing vaccine, but also on overly rosy projections by federal health authorities.
The problems with the egg method have highlighted the push for other vaccine-production approaches, including a cell-based technique that has more than $1 billion of government money behind it.
Initially, the government said 120 million doses of swine-flu vaccine would be available by mid-October. The Centers for Disease Control and Prevention (CDC) reported that nearly 32 million doses had been allocated as of last week.
“It was too optimistic given that it was a biologic product relying on fertilized hens’ eggs,” said Dr. Robert Belshe, director of the Center for Vaccine Development at St. Louis University.
Making vaccine seed using chicken embryos — a method developed more than 50 years ago — might seem quaint, especially in the face of a global flu pandemic. But Bucher said the technique continues to outperform newer approaches. And Dr. Thomas Frieden, the CDC director, called it “tried and true.”
Bucher’s lab received some of the new swine-flu virus only weeks after it was first identified in April. The team came up with a seed for the vaccine 23 days later. The process normally takes at least a month. The seed then was sent in May to the CDC, where it was tested and distributed to vaccine makers.
Manufacturers compared NYMC X-179 with a half-dozen other candidates and found it grew the best, Bucher said. But the flu virus is unpredictable, and manufacturing processes vary.
Bucher said she heard after a few weeks that some manufacturers were having a hard time getting the virus to grow quickly enough. One — Switzerland-based Novartis — initially was able to grow only 23 percent of the virus it normally expected to get from a typical flu vaccine.
“It was a lower-yielding strain than standard,” said Donna Cary, a spokeswoman for Sanofi Pasteur of Swiftwater, Pa., which is using NYMC X-179A to produce about 30 percent of the nation’s H1N1 vaccine, or about 75 million doses. She said Sanofi has improved the yield so it is “now close to standard.”
Novartis, which is contracted to deliver 90 million doses — about 36 percent — to the United States, has had worse problems. It has shipped 7.5 million doses, the company said.
The company is working with a second seed strain that is yielding closer to 60 percent of the standard, spokeswoman Rachel Spielman said.
Given the slow results, many experts are questioning the time-honored method based on eggs. Higher yields can be achieved with a newer technology that grows the virus in cells instead of eggs, Belshe said. The Health and Human Services Department has given vaccine makers more than $1 billion to encourage building cell-based flu manufacturing sites in the United States.
But the cell method remains more expensive than using eggs, he said. Novartis said it expects to open a cell-based flu-vaccine plant in the U.S. this year. But several other companies have abandoned plans for such U.S. plants. Instead, they’ve renovated their egg plants.
Other companies are developing so-called recombinant vaccines using proteins or DNA, but those are in various stages of development and production.
Meanwhile, Bucher and her lab will carry on producing vaccine strains the old-fashioned way. “It continues to be a good way to make vaccine, despite a couple of bumps in the road,” she said. “The virus just loves to grow in eggs.”