Are We Paving the Way to Dig Out of the “Pandemic Hole”? A Narrative Review on SARS-CoV-2 Vaccination: From Animal Models to Human Immunization

Abstract

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a new pathogen agent causing the coronavirus infectious disease (COVID-19). This novel virus originated the most challenging pandemic in this century, causing economic and social upheaval internationally. The extreme infectiousness and high mortality rates incentivized the development of vaccines to control this pandemic to prevent further morbidity and mortality. This international scenario led academic scientists, industries, and governments to work and collaborate strongly to make a portfolio of vaccines available at an unprecedented pace. Indeed, the robust collaboration between public systems and private companies led to resolutive actions for accelerating therapeutic interventions and vaccines mechanism. These strategies contributed to rapidly identifying safe and effective vaccines as quickly and efficiently as possible. Preclinical research employed animal models to develop vaccines that induce protective and long-lived immune responses. A spectrum of vaccines is worldwide under investigation in various preclinical and clinical studies to develop both individual protection and safe development of population-level herd immunity. Companies employed and developed different technological approaches for vaccines production, including inactivated vaccines, live-attenuated, non-replicating viral vector vaccines, as well as acid nucleic-based vaccines. In this view, the present narrative review provides an overview of current vaccination strategies, taking into account both preclinical studies and clinical trials in humans. Furthermore, to better understand immunization, animal models on SARS-CoV-2 pathogenesis are also briefly discussed.

COVID-19 Vaccines: An Updated Overview of Different Platforms

“…After activation in the inductor site, mucosal T and B cells migrate through the lymph and blood to various effector sites, where they differentiate into Th effectors, cytotoxic CD8+ T lymphocytes, and plasma cells [ 56 ]. Mucosal immunity results in the production of specific IgA directly in the mucosa, as well as neutralizing IgG and a specific response of T cells, which reduces the replication of the SARS-CoV-2 virus in the nasal epithelium [ 57 ]. Nasal vaccines are being developed using vectors (adenovirus, Newcastle disease virus, influenza virus, parainfluenza, and respiratory syncytial virus), protein subunits, and live attenuated virus as platforms [ 58 ].…”

Strategies for the development and approval of COVID-19 vaccines and therapeutics in the post-pandemic period

“…For instance, vaccination via inhalation or oral administration is more friendly and acceptable to the elderly and children. [112][113][114][115] Moreover, the selfadministration of such non-invasive vaccines could be feasible, which helps the quick immunization of large populations, especially when encountering pandemics. Heterologous immunization is also recommended to optimize the efficacy of new vaccines.…”