Tag Archives: Science

Risk, statistics and ethics: the AIDS Vaccine

This idea of risk that we have been discussing on TBU for a while now has come up again. The results of a new HIV/AIDS vaccine study were released this week. The Thai trial has shown some promise. The incidence of HIV was 30% lower in the group vaccinated with RV 144 than the control group.

First: the basic bioethics question. Was it OK to give a lot of people a placebo which might let them think they were protected from HIV when they were not at all protected? (Answer: Yes) First-off, they were not told that they were getting an effective drug. They were told they were getting either a placebo or a probably ineffective, experimental vaccine. So the subjects knew beforehand that this shouldn’t be considered a real vaccine.

Second question: why not just give the vaccine to everyone in the study (16,000 people) and compare the effectiveness to the general population? The problem is that you would have a change in HIV incidence that was due to lots of factors. Behavior, knowledge, unknown risk factors (maybe people at higher risk had a greater desire to be in the study than the general population) all could affect the measured efficacy. How would you know which produced your result?

If the vaccine were 100% effective, then there would be no need for a placebo controlled trial. But nothing is 100% effective and – besides – how would you know before you tried?

Now, here’s the more difficult bioethics question: if you have a 30% effective vaccine, who should get it?

This is more tricky. You don’t want to encourage risky behavior (the ‘conservatives’ are always concerned about this). So there is a question to be answered by a careful psychology study: do people modify their behavior after receiving a drug that may or may not prevent a transmissible disease? It seems like they might, but scientists don’t make decisions on “might” if they can avoid it. We make decisions based on what is demonstrably consistent with experiment.

But then it becomes a quantitative statistics problem (more statistics!). It’s only worth vaccinating people if their behavior changes don’t outweigh the efficacy. And then it’s only worth vaccinating people who are at risk… but what if the higher risk people are more prone to behavior modifications? Is is possible to isolate a medium-risk category?

And in all of this, there are massive political problems, not the least of which are form the anti-vaccination people, which I will talk about next week. The vaccine is a real achievement, in any case. Lots of people thought it wouldn’t work. And it reminds us how complicated it gets when trying to do the right thing with imperfect tools.

-Peter

Know your placebo: fight depression with blank pills

The placebo effect is far more interesting than it might seem at first glance. It’s not just lying to oneself. A fake painkiller actually does kill pain, not just convince the subject to say that they feel less pain. So, when the placebo effect gets stronger and overwhelms real pharmaceuticals with good biochemical research to back them, what is a scientist to do?

 

Wired magazine explore the issue. If you’re a medical student, or a scientist you must consider the effect of your control on your interpretation. It’s a common benchmark for drugs to assess efficacy (does it work?) by comparing to a placebo. That’s reasonable. But it’s probably worth also including a null, no intervention control to see how well the placebo works, too, if possible.

-Peter

Our senses lie. Are you sure you will believe it when you see it?

Hot Tipper Rob (after one year, our number 1 supporter!) sent us this amazing little piece about strange multi sensory illusions. There are lots of optical illusions – certain shapes fool our interpretive abilities. What is surprising is that visual stimuli can produce tactile illusions.

So it turns out that if you happen to look at a bunch of horizontal lines moving upward on a screen for a while, then feel a little vibrating line with your fingertip, the line will feel like it’s moving. Evidently, the visual lines predispose our tactile sense to interpret motion.

Here’s another one (via Wired) I found interesting. It’s called the hollow mask illusion and, evidently, it doesn’t work on people with schizophrenia.

I wonder if the Jester would see the mask, or the face?

-Peter

More about bottled water: it may sex you up

Via Wired, it seems that bottled water has some contaminant issues (like that whole scare about polycarbonate water bottles). I still think that leachates are not so great a concern as people think, but most things that will get people to stop drinking bottled water are good ideas in my book.

The study referenced used snails to measure the effects of sex hormone analogues (probably pthalates) that are used as plasticizers in all kinds of things these days. Snails grown in bottled water tended to have a lot more little snails. That is an indicator that there might be some hormone analogues coming out of the plastic.

I doubt the effects on humans will be so easily determined.

Cheers,

Peter

Medical Hypotheses about belly button lint

There’s an article in C&EN that led me to about this article in Medical Hypotheses about belly button lint. A real scientist, Prof. Steinhauser of Vienna University of Technology made a careful study of the stuff. I almost wrote serious scientist, but I think Prof. Steinhauser would agree that he is a funny scientist.

The upshot is that his hypothesis seems to be true: if you have belly hair, you are probably more prone to belly button lint.

The reactions to this 2+ year trial have been mixed. I certainly think he deserves an IgNobel award. That is mixed praise at best. But I will say this: there is a place for frivolous science. Frivolous is not the same as wasteful. A study that is funny, interesting and still rigorous and well designed constitutes a feat.

I would make the analogy of a serious columnist writing a humor piece. It’s still journalism and it’s still an opportunity for good writing. In a similar way, science with a spirit of levity still deserves to be called science.

-Peter