The safety and efficiency of vaccine immunogenicity in infants, adolescents and adults all depends on the immunological and physical differences. Vaccine development can become more efficient by enhancing the innate immune responses to specific properties (Plotkin & Mortimer, 1988). Toll-like receptor agonists are found in multiple vaccine combinations, signifying the importance of a host defense system in an infant compared to an adolescent or adult. The innate and acquired immune systems are both controlled by antigen-presenting cells expressed by Toll-like receptors, which are the potential beginning for future vaccine improvements.

Figure: The immune response from enhanced vaccine immunogenicity.

Neonatal vaccine immunogenicity:
The immune system of both an infant and neonate are the main target sites for vaccine immunogenicity, allowing the contrast between responses to macrophages which are able to stimulate elevated levels of toll-like receptor agonist. The family of toll-like receptors have been thought to help aid an increase in improved strategies for the development of vaccines providing defense against complex antigens (Plotkin & Mortimer, 1988). Therefore, a combination of antigens and toll-like receptor adjuvants encourages protective immunity to both infants and neonates. Therefore, vaccine developments are required for more effective protective immune responses earlier in life.

Adolescent vaccine immunogenicity:
The maturing immune system after puberty is regulated by sex steroid hormones that affect both the innate and acquired immune system, indicating that vaccine immunogenicity for adolescents and adults is a gender-dependent difference (Plotkin & Mortimer, 1988). The innate-immune system responds to an invasion focussing on the elimination of pathogenic microorganisms from defense mechanisms leading to the understanding of how vaccines in adults and adolescents are involved in different immune defences.

Aging vaccine immunogenicity:
Vaccine development and designs can be improved by understanding the developmental expression of the innate immune pathways, leading to enhancing the activation of the adaptive immune system. An important determinant of vaccine enhancement is the ability of a given vaccine to activate the innate immune system by enhancing the antigen-presenting cells which function by adaptive responses. Adjuvants are important components of modern vaccines as they are able to increase the immunogenicity and solubility of recombinant proteins to specific pathogens (Plotkin & Mortimer, 1988). The optimal vaccine formulation to target dendritic cells, is one that provides a more efficient stimulus by inducing the maturation of dendritic cells and thereby enhancing the adaptive immune responses. Whereas, prime-boost immunisations allow the development of improved vaccines which are more effective and efficient for preventing serve diseases.

Vaccine DevelopmentNeonatal Immune System : Adolescent Immune System : Adult Immune System´╗┐´╗┐´╗┐References Contributed by Rana Hammoud