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Updated Thursday, June 25, 2009 11:02 am TWN, By John M. Barry, Special to The Washington Post

Pandemic reality check for H1N1

However, the usefulness of non-pharmaceutical interventions is limited, and even if they work, their chief impact will be to flatten the pandemic's peak and stretch out the duration of a wave of illness to make it easier to handle. Consider: Those telecommuting are likely to run into Internet capacity problems, while the impact of closing schools — aside from the burden that creates on working parents and their employers, or on children who get good meals only at school — depends on how much kids congregate while out of school. And sustaining compliance will be both important and difficult. Scholars Bradley Condon and Tapen Sinha found that in Mexico City this spring, when the government advised wearing masks on public transportation, compliance peaked at 65 percent three days later — but declined to 26 percent only five days after that. This decline came even as the government was taking the extreme measure of closing all nonessential services and businesses. Such behavior does not portend well for sustained compliance with any measure.

The most important human intervention is, of course, a vaccine. There are many unknowns: Because influenza mutates so rapidly, a new vaccine has to be made each year just for seasonal flu. Vaccines for most diseases approach 100 percent effectiveness, but a good flu vaccine is 70 percent effective; a great one is 90 percent effective. The vaccine in the 2007-08 flu season was only 44 percent effective. Hitting the “good” mark for a new virus that may be changing even more rapidly than seasonal flu will be difficult.

Supply is another problem. In a best case, enough vaccine for the entire U.S. population could be available by October as long as an adjuvant is used to simultaneously stimulate the immune system, which lessens the need for antigen from the virus itself. However, if the virus used to make vaccine grows slowly, or if a dose requires more antigen than seasonal flu, or if two doses are required to provide protection, producing that much vaccine could easily stretch deep into 2010. In addition, only about 30 percent of the supply will be made in the United States. The more virulent the virus, the more likely it is that foreign governments will refuse to allow export of the vaccine until their own populations are fully protected.

Meanwhile, the emergence of the H1N1 virus in no way lessens the threat from H5N1, more commonly known as bird flu. And the same day the World Health Organization declared H1N1 a pandemic, Egypt announced 25 new human cases of H5N1 — the largest number yet identified in a single day.

The bottom line? Little can be done in the short term beyond exerting diplomatic pressure to guarantee that foreign governments allow manufacturers to honor contracts to export vaccine. In the medium term, sustained investment in vaccine production technologies — especially recombinant ones — could make it possible to produce massive amounts of vaccine in a few weeks. In the long term, we need a vaccine that works against all influenza viruses. Enough work has been done to suggest that this Holy Grail is achievable. Had influenza been taken seriously for the past 30 years, we would probably have one by now. No matter what happens over the next year or two, that's one history lesson we need to learn.

John M. Barry is a distinguished scholar at the Center for Bioenvironmental Research at Tulane and Xavier Universities and the author of “The Great Influenza: The Story of the Deadliest Pandemic in History.”

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