Rationale and Impact of MACIVIVA
With few exceptions, commercialized vaccines are generally delivered by injection through the intramuscular or subcutaneous route. Vaccines contain immunogens classically found within a large variety of biological compounds such as peptides, proteins, glycoproteins and sometimes carbohydrates and lipids. These immunogens may trigger the immune system for producing antibodies and/or cytotoxic T cells for preventing the pathogen transmission or blocking and/or slowing down the disease progression.
However, these vaccines generally exist as liquid formulation that are inherently prone to physical and/or chemical modifications. The cold chain storage is still fundamental for preserving the bioactivity of most liquid and freeze-dried vaccines. For reconstituted freeze dried vaccines, they harbor important instability and must be used within hours and kept refrigerated. Vaccine degradation generally takes place during shipment and/or storage of liquid or lyophilized products, which may affect the immunological properties of the immunogens, with unwanted immune responses or insufficient immune protection. There is growing evidence that solid dosage formats (e.g. powder form) for vaccines may offer several advantages over the liquid formulations, such as the prevention of molecular motion and shear-induced degradation, and slowing down modifications and degradation reactions involving water and oxygen radicals, resulting in improved stability, enhanced shelf-life of vaccines and greatly simplified logistics.