Top-level science through the eyes of an expert.

Vaccination is one of the most effective and affordable ways to save 2 to 3 million lives every year. Even though critical issues on vaccine effectiveness and acceptability still remain under discussion, innovative approaches, such as virus-like particles and inactivated vaccines, are currently being explored to conquer Hepatitis, Dengue and Influenza, HIV, Malaria and Tuberculosis.

While vaccination increasingly relies on basic research to understand and translate human immunity, the field is at a turning point, with new ideas and innovations. Two aspects have been added: the prediction of intensity of immune responses through systems biology approaches and the development of alternative routes of immunization for increased efficacy. Most current vaccines are administered by intramuscular or subcutaneous routes. However, intradermal and transcutaneous techniques are regaining popularity, thanks to:

• the rationalization of targeting of the different cutaneous layers, i.e. the epidermis, dermis, or hypodermis
• advances in knowledge about the plasticity of antigen-presenting cells (Langerhans cells, dermal dendritic cells and dermal macrophages), which allow proposing rational immunization procedures.

In addition, the recruitment of inflammatory cells, such as neutrophils in the dermis, impacts the localization and quality of adaptive immunity. The rationale of various vaccination strategies can be discussed by compiling immune-monitoring, bio-modeling and systems biology approaches.