Children Vaccines

Vaccine Delivery Technologies

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There are currently several factors that are creating pressure to improve delivery systems for vaccines. First, in the current regulatory environment, there is a growing requirement to develop vaccines that are very well defined in molecular terms. Thus, as opposed to using whole-inactivated pathogens presenting a complex range of antigens, most newly developed vaccines are rather based on selected target antigens. In some cases these may be single molecules, or even fragments thereof, derived from an infectious micro-organism, a tumour cell, an allergen or an auto-antigen. The target molecule may be administered as a purified protein or as a peptide(s), or may be expressed from plasmid DNA or a recombinant virus. Often, such molecular vaccines are poorly immunogenic, implying a need for an adjuvant, a specific formulation or a vector system of enhanced immunogenicity1. Second, although in the past most vaccines have been designed to stimulate antibody responses against surface molecules of bacteria or viruses, new generation vaccines are increasingly designed to elicit cellular immune responses, especially of the Th1 type. Such responses are considered paramount for targeting chronic infectious diseases that may have an intracellular stage (associated for example with HIV1, herpes viruses, hepatitis C virus, Helicobacter pylori, Plasmodium falciparum, Mycobacterium tuberculosis), but also for the development of therapeutic vaccines against cancer, autoimmune diseases or allergies2. New vaccines are also being developed to elicit mucosal immune responses in humans, for example to protect against pathogens such as influenza virus, HIV1, HSV or human oncogenic or wart-associated papilloma viruses. Unlike most of the traditional vaccines, these efforts require the recruitment of cellular or mucosal immune effector mechanisms and necessitate the exploration of new routes of administration, new formulations, and new adjuvant systems3. Third, improving vaccine administration generally, either for the physician, or more importantly for the customer, towards pain-free and safe needle-less devices is likely to represent a major driver in the future vaccine market.