Parenteral Vaccine Administration: Tried and True

Abstract

The majority of current and traditional vaccines have been administered by injection into or under the skin. Most of the utilised historic vaccines as well as many of the current vaccines are live or attenuated bacterial or viral preparations, which possess integrated adjuvant properties and their particulate nature enables these vaccines to efficiently drain to secondary lymphatic organs or to activate the innate immune system to carry the vaccine to the next draining lymph node. However, live vaccines are getting rarer and modern vaccines are typically subunit vaccines comprising of synthetic peptides, recombinant proteins or nucleotide-based vaccines such as mRNA and plasmid DNA. While the safety profiles of subunit vaccines are good, their immunogenicity is often poor for which reason new and stronger adjuvants are required. Another possibility to improve the immunogenicity, function and efficacy of such new vaccines is to facilitate targeting to secondary lymphatic organs. Adjuvants and synthetic particles can enable such targeting to some extent, but the use of recombinant bacterial or viral carrier systems is typically more effective. However, a considerate choice of vaccine administration route is also crucial in the development and marked release of new or improved subunit vaccines. In the following, we will discuss the potentials and limitations of various parenteral vaccine administration routes.