Mechanism of Action, Efficacy and Safety of Anti-SARS-CoV-2 Vaccines: An Overview

This chapter evaluated the mechanism of action of each vaccine as well as the efficacy, the safety and the storage temperature.This study takes into consideration the principal vaccines developed against the SARS-CoV-2 in this unprecedented period of Covid-19 pandemic. Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection causes coronavirus disease-19 (COVID-19), which is characterized by clinical manifestations such as pneumonia, lymphopenia, severe acute respiratory distress, and cytokine storm. In addition, the problem of the dose units, the vaccinal strategy, the activity of alternative compounds such as the monoclonal antibodies and especially the issue of the virus variants were also described in detail. The existing treatment methods such as antiviral drugs (remdesivir), antibodies (intravenous hyperimmunoglobulin therapy), anti-inflammatory drugs (statins, dexamethasone), immunomodulatory therapies, anticoagulants, and antifibrotics are reported to exhibit different therapeutic efficacies during COVID-19 treatment. Four vaccines are currently used in Italy: Pfizer-BioNTech mRNA BNT162b2 (Comirnaty) (USA), Moderna mRNA 1273 (USA), Astra-Zeneca ChAdOx1-S (recombinant) viral vector adenovirus belonging to Oxford (UK) and Pomezia (Italy), Janssen (two recombinant viral vector adenoviruses) belonging to Johnson & Johnson (USA). The efficacy of Pfizer and Moderna for preventing disease or severe disease results 95–87.5% and 94.5–100%, respectively. Astra-Zeneca and Janssen's efficacy are roughly 70% and 65%, respectively; for Janssen, it varies by region and ranges from 72% to 57%. It is also discussed how the administered dosages (one dose, two doses of the same vaccination or two doses of a different vaccine, and half dose) should be handled. The age-based immunisation technique continues to be the easiest, clearest, and most equitable criterion. This strategy is also based on accelerating the administration of the vaccines, so that as many subjects as possible can be vaccinated quickly for achieving the “herd immunity”. The vast majority of approved vaccines was traditionally focused on the induction of strong protective neutralizing antibodies against the target pathogen, thus aiming to confer sterilizing immunity in vaccinated individuals. For the treatment of Covid-19 disease, monoclonal antibodies seemed to be an effective option. Bamlanivimab and etesevimab are two antibodies that the FDA has just approved. They could also be utilised to spread viral variant infections, which pose a serious threat because of their increased virulence and transmissibility and weaker immune system.