Flu Vaccine Shortage Posts From 2004

I am reposting several posts I wrote in 2004 at Get Real during the flu vaccine shortage.

Ethics of the Flu Vaccine Shortage: What Would Network Science Do?

The flu vaccine shortage has brought to high relief the inability of our government to effectively respond to public health threats. This is the result of a laissez faire attitude toward the safety net that the government has an implicit obligation to put and keep in place for the old, young, and needy, but even more chilling, as the direct result of outdated ethics.

Confronted with a shortage of flu vaccine, the health care apparatchiks have responded in a 19th century, “women and children first” approach, which may feel like the ethical response, but is in fact not well-grounded scientifically. It turns out that doling out the scarce flu vaccinations to those most at risk will not counter the threat of epidemic. The government bureaucrats may continue in the old, wrong-headed, and unscientific rhetoric, but the public heath people should know better.

Network science has shown that human interaction is scale free: that is to say, some of us have significantly more contacts that the rest of us. As scale-free networks grow, those with more contacts are more likely to add new contacts. This is the power law of popularity and influence that we have seen at work everywhere in human interactions.

Research into the spread of diseases like AIDS has suggested an alternative approach to breaking the non-linear expansion of the epidemic, which diffuses through the population just like innovations:

[from Linked by Albert-László Barabási]

Despite differences in purpose and detail, all diffusion models predict the same phenomenon: Each innovations has a well-defined spreading rate, representing the likelihood that it will be adopted by a person introduced to it. […] Yet knowing the spreading rate alone is not sufficient to decide the fate of an innovation. For what we must calculate is the critical threashold, a quantity determined by the properties of the network in which the innovation spreads. If the spreading rate of the innovation is less than the critical threshold, it will die out quickly. If it is over the threshold, however, than the number of people adopting it will increase exponentially until everybody who could use it does.

Recognizing that passing a critical threshold is the prerequisite for the spread of fads and viruses was probably the most important conceptual advance in understanding in spreading and diffusion. Currently the critical threshold is part of every diffusion theory. Epidemiologists work with it when they model the probability that a new infection will turn into an epidemic, as the AIDS virus did. […]

For decades, a simple but powerful paradigm dominated our treatment of diffusion problems. If we wanted to estimate the probability that an innovation would spread, we needed only to know its spreading rate and the critical threshold it faced. Recently, however, we learned that some viruses and innovations are oblivious to it.

Research into the spread of computer viruses has led to a new, network science-based approach to modeling — and countering — human epidemics.

[from Linked by Albert-László Barabási]

The deadly virus [AIDS] must have followed the route already spotted in the spread of innovation and computer viruses: Hubs are among the first infected thanks to their numerous sexual contacts. Once infected, they quickly infect hundreds of others. If our sex web formed a homogeneous, random network, AIDS might have died out long ago. The scale-free topology of AIDS dispersal allowed the virus to spread and persist.

So the problem before us, ethically, should not be “find those who are the most at risk, and vaccinate them,” but rather “who among us are most likely to be the hubs in the spread of the flu? Find them, and vaccinate them.”

Especially when supplies are limited, the best hope to stem the rise of the epidemic is to find the most connected individuals in the population — which in this case means physically connected, not virtually — and immediately vaccinate them.

I am no expert in the determination of who are the most connected people, but it would likely include some obvious — and non-obvious — walks of life. Various kinds of public and health service workers come to mind: doctors, nurses, and other folks in hospitals, clinics, and medical offices who come in contact with the old, young, and infirm are obvious candidates. Starbucks barristas, taxi cab drivers, and bartenders — while not at risk, necessarily, to succumbing to the flu — are likely disease vectors who might spread the disease to hundreds of others if they were to contract it. I am even willing to concede that our Senators and Representatives to Congress are likely to fall into this group, and therefore administering vaccine to this group is in the public interest, even while it may appear to be self-serving.

While some have argued that administering AIDS counteragents (we still have no vaccine) to those who are most promiscuous only rewards unsavory and immoral behavior, we have no such quandary in this case. The flu is not a sexually transmitted disease, so there is no moral dimension to vaccinating the bus driver: he could infect hundreds of old, young, and infirm every day. And he would do so simply through doing his job, not through some arguably anti-social act. And worst of all, he could infect two dozen other bus drivers, who would infect thousands, again.

The scale-free network is there, we all know it, and you can’t wish it away. Our best choice is to apply what we know.

The stupidity du jour is the bone-headed notion of vaccine lotteries. This is totally dumb, and intelligent people everywhere should rise up against its apparent “fairness.” It flies in the face of reason, and squanders perhaps our only chance to stop the spread of the flu in a population confronted with an inadequate supply of vaccine.

The outcome of better science should be the betterment of society, on the whole, and an improvement in every individual’s life. However, this is only true if those that govern our collective resources wisely take into account the best scientific thought. If they, on the other hand, disregard science and devolve into outdated ethics and pseudo-scientific mumbo gumbo, they should be hounded from office.

More on Flu Vaccination: Kids are the Supernodes

I posted a plea for the application of network science to the distribution of flu vaccine, last week. Various Corante contributors pointed out some fallacies in my arguments, or at least the fact that my arguments are not well supported by network research to date.

Both danah boyd and Clay Shirky pointed out via email that the studies I cited re: AIDS dispersal were much simpler to model because of the relative difficulty involved in spreading AIDS. The flu, on the other hand, is spread by very casual interaction — breathing other person’s exhalations, or using a cup touched by a flu sufferer — so that the dispersal is much more general and open.

I concur, as far as the analysis goes. But I maintain that there is still a network gradient involved, and that people should be sorted out to those least likely to spread the disease — older shut-ins, for example — and those who are more likely to spread the bug.

Renee Hopkins Callahan came across an interesting support for this position:

[from NPR : Health Experts: Kids Should Get Flu Shots First]

Health Experts: Kids Should Get Flu Shots First

Morning Edition, November 1, 2004 · In a typical flu season, more than 40 percent of school-age kids get the flu. But health officials are trying to get the vaccine to Americans over age 50. New findings suggest children should be vaccinated first to reduce the spread of flu to older adults. Hear NPR’s Richard Knox.

Turns out that kids get the flu at over 7 times the rate of adults, and then infect at risk adults. As Renee notes, “This test is based on a case in Japan where flu in older people almost disappeared after a period of years of vaccinating all school-age children, then returned after the vaccination program was discontinued.”

So the empirical results suggest that vaccinating school age children may break the epidemic explosion, because schools turn out to be a hot zone for the disease, even though the children themselves are not at risk. So, when we are short of vaccine, we should target the kids to quell the epidemic. Of course, as is noted in the report, if you really are confronted with a pandemic, you should inoculate nearly everyone, but if you inoculate even 25% of the kids, you will see a drastic downturn in the overall infection in the population as a whole.