Imperfect vaccines and imperfect models

A recent paper by Gandon et at presents a model for how leaky vaccines can lead to evolutionary changes in the virulence of parasites. Whilst readers of some of the press reaction to this paper might be forgiven for thinking that it referred to certainties about actual malaria vaccines, there are currently no malaria vaccines beyond the early clinical trial phase, so the paper could in principle offer no more than theoretical predictions. The models might well be less appropriate for the chosen example of Plasmodium falciparum malaria than for other parasites. Critical review of the Gandon et at paper highlights both the fact that the determinants of virulence in malaria are not well understood, and that monitoring of malaria vaccines should consider more than just the immediate effects on vaccine efficacy.