The long-running saga of Elan's attempt to come up with a vaccine for Alzheimer's disease continues. There have been bold attempts, setbacks, rethinks, more setbacks, and now they're starting up again. Dosing of the latest version of their vaccine against the beta-amyloid protein, known as ACC-001, was suddenly halted in April when one patient came down with a skin lesion which was thought to be possibly autoimmune-linked vasculitis.

Biopsy results didn't confirm that, though, and the Elan/Wyeth partnership is resuming clinical studies. I'm not sure what that couple of months has done to their trial design; I assume that they've just started enrolling new patients and will continue with them, while continuing to monitor the former dosage groups. Maybe, though, there's a way to continue with some of those people and not lose all the time, effort, and data.

The idea of an amyloid vaccine has always excited and alarmed me in equal measure. But that's how I feel about the immune system in general, come to think of it. We have enough cellular firepower to completely destroy ourselves from the inside out - keeping that on a leash to where it (mostly) only goes after what it's supposed to is extremely impressive.

Now, I think that the usual sorts of vaccines are one of the great public health advances of civilization, but they work so well because they're targeted to outside agents (viral coat proteins and the like). Even so, there's a disturbingly large part of the population that remain suspicious of all vaccinations - I say "disturbing" not least because if that population gets too large, the efficacy of vaccination in general could be crippled. But what will these people think about a vaccine that's targeted to an endogenous protein? My immunology may need brushing up, but I can't think of any other example of such.

One thing that may keep this from becoming a huge issue, though, is that an amyloid vaccine, if it succeeds, will be targeted at the elderly rather than at children. And it'll be something that will have an effect against a disease that everyone can see right in front of them, rather than preventing diseases that most people have only read about in books. We'll be back at the situation that prevailed when the polio vaccine was introduced: no one had much doubt that the vaccine was better than the disease.

But even a vaccine fan like me still has room to admire, from a distance, the nerve of this approach. The brain is a special case, immunologically, and letting slip the dogs of war in there is not an intrinsically safe idea. But Alzheimer's is an intrinsically nasty disease. . .