Sizing the optimal dimensions of a vaccine delivery system: a particulate matter.

Encapsulation of subunit antigens into particulate vaccine delivery systems is a promising strategy to enhance their immunogenicity. The most basic physical parameter of these particles, their size, has a profound effect on the immunogenicity of the vaccine. Interestingly, the optimal particle size varies depending on the desired type of immunological memory and the route of administration. In this editorial, we draw attention to the effect of particle size on the resulting immune response and accentuate the importance of adequate particle sizing methods, within and beyond the intended size range of the delivery vehicle, to assess vaccine quality.