Friday, May 01, 2009

Why There's No Swine Flu Vaccine

By Robin Lloyd, LiveScience Senior Editor
There is a flu vaccine ready for us, thanks to the federal government and its pharmaceutical partners. A total of 13 million doses are stockpiled. Unfortunately, it's for the wrong virus. For now, at least.

Researchers and policy-makers placed their bets a few years ago on the H5N1 strain of bird flu virus emerging in Asia (the highly lethal virus is hard to pass from birds to humans but still has killed 257 people in recent years). Preparations were made for this bird flu to go pandemic, that is, to transform into a global outbreak that spreads easily from person to person and sweeps across regions of the world in a short time. Four years after the first vaccine doses were licensed by the Food and Drug Administration, no pandemic has occurred.

What we have on our hands instead this spring is an outbreak (not a pandemic, as of Wednesday morning) of an H1N1 swine flu virus strain, not emerging from Asia at all.

So it's back to square one.

The Centers for Disease Control and Prevention (CDC) has started the early work on a vaccine for the new swine flu to protect us from getting sick or at least deathly sick. (The so-called seasonal flu shots that some people get every winter won't do the job.)

"We're growing up that seed stock of virus so that if we decide to manufacture a vaccine, we are ready to do so," CDC Acting Director Dr. Richard Besser told reporters Tuesday. "And that's moving forward. We're moving forward aggressively so that if a decision is made that we need to rev up production to make that vaccine, we would be ready to do so.

Once researchers and manufacturers commit to making a vaccine for the new swine flu virus in humans, it will take four to six months to be ready.

"Even though there is something in the works doesn't mean that you can push a button and out of a spigot is going to flow vaccine," said Christine Layton, a public health researcher who specializes in pandemic influenza preparations, vaccines and immunization infrastructure. She co-wrote a five-part report in 2005 ago that pointed out limitations to the nation's flu vaccine-making system. Layton works for RTI International, a research institute in North Carolina's research triangle.

"I think the issues that have yet to be defined are basically figuring out exactly how a vaccine is going to be manufactured, and we sort of have gone from thinking about a potential pandemic to thinking, 'This could be the big one,'" Layton told LiveScience. "And it's my understanding that processes have already started in terms of isolating the influenza virus and starting to try and do what's necessary to ramp up influenza vaccine production."

Missteps in flu vaccine policy are nothing new, and they are easy to make. The H5N1 avian flu vaccine might still be needed if a pandemic breaks out as the virus mutates over the years, which some experts still anticipate.

But here are some reasons why it's hard to make a magic bullet against the new swine flu, or any flu, in time to make a difference:

Behind the times

The truth is there aren't that many vaccines, compared to all the stuff that can make us sick. There are about 1,400 known different human infections. They are caused by microparasites — viruses, bacteria, fungi and protozoa, explains Penn State biologist Peter Hudson.

"In the U.S., we've only got about 55 vaccines against something like 23 diseases," Hudson told an audience at the American Museum of Natural History earlier this month. "That's only about 2 percent, and then those cause us significant problems at times because they generate a selective pressure that can result in rapid evolution away from the selective pressures that vaccines may give us."

The seasonal flu vaccine and the stockpiled vaccine against the H5N1 strain of bird flu virus are two of those vaccines.

The U.S. flu vaccine manufacturing system is a partnership between the federal government and various drug-makers, such as GlaxoSmithKline, Novartis, Sanofi Pasteur and MedImmune. The whole multi-tiered system is detailed by Layton and colleagues in the report for the U.S. Department of Health and Human Services' Assistant Secretary for Planning and Evaluation.

The report — focusing on the annual vaccine for the "seasonal flu" we all face every winter — is based on information gathered from confidential interviews with 30 "key informants" ranging from federal, state and local health officials to vaccine manufacturers and wholesalers to health care workers.

One major conclusion: there wasn't even enough capacity to make the doses of vaccine needed for seasonal influenza shots for the elderly and health care workers and others who requested it, "so certainly there needed to be better preparedness in terms of coming up with a pandemic vaccine," Layton said.

Since then, some significant improvements have been made, she said. There are now six manufacturers of seasonal influenza vaccine, rather than three, which means the health care system is less dependent if something goes wrong with vaccine production at one pharmaceutical company. This happened at Chiron in 2004–2005, when the UK government shut down vaccine production at the company, leaving the United States high and dry. Chiron had been set to provide half the nation's seasonal flu vaccine that year.

Also, more companies now have received funding from the National Institutes of Health (NIH) to pursue the development of new approaches to making vaccines, Layton said.

One of the hold-ups with developing a new vaccine is simply growing live cell cultures that have the infectious virus growing in them.

"Anyone who has gardened or worked with making bread that requires yeast knows that there is only so much you can control," Layton said. "There is the part that is up to nature or luck, in terms of getting the yields."

Vaccine for the 'wrong virus'

Although some researchers have figured out how to predict where the next infectious disease will emerge, it is harder to predict, if not impossible to predict, which type of disease, such as influenza versus cholera, will emerge. And within influenza, it's another big guess as to which strain of influenza will cause the next outbreak or pandemic.

Based on early signs when bird flu first started killing people and making others sick in 2003, the vaccine policy community suggested a vaccine for humans against the H5N1 strain of the virus causing bird flu. Pharmaceutical manufacturers got to work developing the vaccine.

In 2007, the FDA announced the vaccine was licensed and ready for use as part of the nation's stockpile.

It was "not an unreasonable assumption" to think that the next pandemic would be an avian flu emerging in Asia, Layton said. "Two of the last big pandemics in the century arose in that area. For a variety of environmental and biological factors, that is often where influenza evolved."

Public health experts and officials knew it was a gamble. "If the [next] pandemic virus strain is substantially different from the H5N1 virus contained in the vaccine, it is unlikely that the existing vaccine would be effective," the FDA wrote in a 2007 question-and-answer sheet on its Web site, announcing the vaccine's availability. "It is possible that the next influenza pandemic will be caused by a strain of influenza that does not belong to the H5N1 subtype. Both of these scenarios would require development of a new vaccine."

Layton defends the public health community's effort, though.

"As much a people might complain and say, 'Why did we spend all these resources on making an H5N1 vaccine, thinking that was the pandemic, and it's useless for this situation?' we have to bear in mind you can't really make a pandemic vaccine until you know the strain that causes the pandemic, rather than think this is wasted money," Layton said.

Also, the effort gave manufacturers a practice run at ramping up the capacity and mechanisms to actually produce millions of doses of a new flu vaccine for a potential pandemic, she said. Hopefully, that will benefit the world in the coming months if a swine flu vaccine is called for.

Is natural immunity possible?

It's cold comfort but scientifically true that the other way to gain immunity is natural exposure — getting sick from the virus and surviving it, like with any cold virus.

That which doesn't kill me makes me stronger — this is a fair account of our bodies' immune systems. The new swine flu is not thought to be highly fatal — around 1 to 4 percent of infected people are expected to die. But if it infects a lot of people, in the millions, deaths mount. Not to mention that millions of simply sick people requires a lot of hospital and medical care and lost time at work, and so a pandemic would have huge economic repercussions.

No one knows how quickly you can acquire immunity from the new swine flu if exposed to it, but with flu shots, it takes about two weeks to have sufficient immunity to be protected when exposed to the actual virus, Layton said.

That's why seasonal flu shot programs are usually launched in the fall before the viruses tend to spread more widely in the winter.

"By the time you have recuperated, say a week or something, your body is going to have enough of the antibodies to be protected," Layton said.
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