Difficulties producing H1N1 vaccine calls time-honored method into question


VALHALLA, N.Y. — Most of the world’s H1N1 vaccine started in
30 chicken eggs kept here in a warren of cluttered labs at New York Medical

Working seven days a week, microbiologist Doris Bucher and
her eight assistants made “seeds” that manufacturers around the globe
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.

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 just 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 reported that nearly 32 million doses had been allocated as of

“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 last week, 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. Normally, the process takes at least a month or
longer. The seed was then sent in May to the CDC, where it was tested then
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
notoriously 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, the 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 that it is
“now close to standard.” The company was never behind in its promised
production, she said.

Novartis, which is contracted to deliver 90 million doses —
about 36 percent — to the United States, has had worse problems. So far it has
shipped 7.5 million doses, the company said.

The company is now working with a second seed strain that is
yielding closer to 60 percent of the standard, said spokeswoman Rachel

Still, 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 U.S. 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 for manufacturers
than using eggs, he said. Novartis said it expects to open a cell-based flu
vaccine plant in this country later this year. But several other companies have
abandoned plans for such plants here. Instead, they’ve renovated their egg

Other companies are developing so-called recombinant
vaccines using proteins or DNA, but those are still in various stages of development
and production.

In the meantime, 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.”

Via McClatchy-Tribune News Service.


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