Human immunodeficiency virus vaccines

An Outline of the Immunogenic Potential of Progressing SARSCoV- 2 Vaccine Technologies among Children and Adolescents

BACKGROUND

SARS-CoV-2, a highly dynamic beta-coronavirus, can afflict all age groups. Notably, over 16100 mortalities have been recorded among children as yet. In this regard, many vaccine projects are operational to assess immuno-potency among young cohorts. A bulk of reports have evidenced the efficacy of these immunization technologies in the elderly population, though the impact is yet to be determined among children.

OBJECTIVES

This review is envisioned to outline the current efficacy of contributing vaccine technologies and examine the dose-dependent impact of immunization regimens in lowering the risks of SARS-CoV-2 infections among children and adolescents. Furthermore, the current review exclusively estimated the vaccine impact at current doses.

METHODS

A total of 52 research papers extracted from PubMed, Pubmed Central, Science Direct, Research Gate, Google Scholar and Semantic Scholar were screened along with an emphasis on patents. Inclusion criteria involved all published reports directly or indirectly linked to the contributing vaccine candidates that are operational among the young cohort. Unrelated research papers were excluded from the study. Key search terminologies included information on vaccine identifiers, such as name, type and clinical trial ID, and successively restricted to children and adolscents age groups.

RESULTS

Several vaccine designs, such as mRNA-based vaccinations, viral vector vaccines, DNA vaccines, inactivated vaccines, recombinant vaccines, and protein-based immunizations, are being examined at various stages of clinical trials to gauge the effects on children and adolescents. With reference to the published reports, the mRNA 1273 (1610 GMT; 6-10 yrs, 1401 GMT; 12-15 yrs), BNT162b2 (1407 GMT; 6 months- <2 yrs, 1535 GMT; 2-4 yrs, 4583 GMT; 5-11 yrs, 1239.5 GMT; 12-15 yrs) and Ad5 nCoV (1037.5 GMT; 6-17 yrs) offered relatively high neutralization titers with sharp seroconversion rates compared to MVC-COV1901 (648.5 GMT; 12-17 yrs) and ZyCoV-D (133.49 GMT; 12-17 yrs), which produced modest immune responses.

CONCLUSION

Currently, the WHO is analyzing emerging evidence to issue an emergency use list of vaccines for vaccinating children and adolescents.

Mucosal Vaccination: A Promising Alternative Against Flaviviruses

The Flaviviridae are a family of positive-sense, single-stranded RNA enveloped viruses, and their members belong to a single genus, Flavivirus. Flaviviruses are found in mosquitoes and ticks; they are etiological agents of: dengue fever, Japanese encephalitis, West Nile virus infection, Zika virus infection, tick-borne encephalitis, and yellow fever, among others. Only a few flavivirus vaccines have been licensed for use in humans: yellow fever, dengue fever, Japanese encephalitis, tick-borne encephalitis, and Kyasanur forest disease. However, improvement is necessary in vaccination strategies and in understanding of the immunological mechanisms involved either in the infection or after vaccination. This is especially important in dengue, due to the immunological complexity of its four serotypes, cross-reactive responses, antibody-dependent enhancement, and immunological interference. In this context, mucosal vaccines represent a promising alternative against flaviviruses. Mucosal vaccination has several advantages, as inducing long-term protective immunity in both mucosal and parenteral tissues. It constitutes a friendly route of antigen administration because it is needle-free and allows for a variety of antigen delivery systems. This has promoted the development of several ways to stimulate immunity through the direct administration of antigens (e.g., inactivated virus, attenuated virus, subunits, and DNA), non-replicating vectors (e.g., nanoparticles, liposomes, bacterial ghosts, and defective-replication viral vectors), and replicating vectors (e.g., Salmonella enterica, Lactococcus lactis, Saccharomyces cerevisiae, and viral vectors). Because of these characteristics, mucosal vaccination has been explored for immunoprophylaxis against pathogens that enter the host through mucosae or parenteral areas. It is suitable against flaviviruses because this type of immunization can stimulate the parenteral responses required after bites from flavivirus-infected insects. This review focuses on the advantages of mucosal vaccine candidates against the most relevant flaviviruses in either humans or animals, providing supporting data on the feasibility of this administration route for future clinical trials.