Valuable data on patients' responses to a candidate vaccine for treating Alzheimer's disease may never be collected, now that the San Francisco arm of Elan has abandoned its trial (see page 715). The case highlights a quandary that can occur when scientifically interesting trials run out of commercial promise. The issue doesn't arise with most trials of drug therapies or medical devices, as these have no further biological influence when the trial is over. But the vaccine trial is different: long-term follow-up might shed light on the pathological consequences of Alzheimer's vaccines.

In January 2002, Elan stopped its trial of a vaccine against the amyloid-β protein, a major constituent of the destructive brain plaques that occur in Alzheimer's, after some patients suffered brain inflammation. But many of the participants developed antibodies to amyloid-β, and these are still biologically active.

Elan reported the results of the trial, taking into account clinical data gathered until December 2002. But only one of the 28 medical centres that provided patients for the trial continues to study its patients systematically — and preliminary results suggest that the course of progress changes in the second year of immunization.

A group of patients with antibodies to amyloid-β is a unique resource. But who should organize, and pay for, the monitoring of the group? Elan won't do it and the US Food and Drug Administration says it has no jurisdiction over what happens when a trial ends early. It will intervene only if a company is close to licensing a product, as it did, for example, to insist on the long-term monitoring of patients in gene-therapy trials. It says that placing the burden of responsibility on companies such as Elan would be a disincentive to innovation. Research funding agencies, such as the US National Institutes of Health, are also disinclined to finish off the trials of others.

Funding agencies should be more sympathetic to grant applications from researchers in participating centres who are willing to take on the onerous task of monitoring the progress of patients scattered around the world. Such work may not be particularly innovative, but it could yield important health benefits and so deserves support.