The need for a new definition for vaccine

Background and purpose: The vaccine is classically defined as a biological preparation that induces an immune response for protection against infection and disease. However, this mode of action has disadvantages. In this article, some disadvantages of the immune-based action of vaccines are mentioned and then a new generation of the vaccines is proposed. Materials and methods: A review of articles in the PubMed using some keywords such as "vaccine", "vaccine delivery systems" and "vaccine platforms". Results: Some challenges with current vaccines include having mild systemic and local adverse effects due to activating immune responses, not being beneficial to the individuals with immunodeficiency disorders, the effect of antibody-dependent enhancement of infection, reducing vaccine effectiveness after viral mutations because of the dependence of immune response induction on the viral structural proteins with less conserved genetic sequences, inducing antigen-specific immune tolerance and delayed immune-activation (usually two weeks) which during that, the virus may replicate in the host cells. Moreover, vaccines do not directly target the viral replication inside the host cell. As long as the virus-producing cellular factory is active, the immune response will be inefficient, especially for viruses that have a fast replication rate such as the Delta variant of severe acute respiratory syndrome coronavirus ۲ (SARS-COV-۲). This variant with faster replication and higher viral load needs four hundred times higher neutralizing antibody titers compared to the ancestral variants .Conclusion: All above-mentioned instances prove that immune system-based action of vaccines has a limited efficacy and highlight a need for a new generation of vaccines which able to act independently of the immune system. Nevertheless, since the viral proteins are multifunctional, a good vaccine candidate should be multifunctional too. The future vaccines may be some intracellular vaccines, which directly target proteins involved in the viral genome digestion (e.g. endonucleases) as well as activating immune responses. However, protecting the host cell genome is also a priority. Also, these types of vaccines may encode DNA methyltransferases in order to protect the host DNA. At the end, the immune system response to vaccine-containing cells should also be considered.