An Updated Review of SARS-CoV-2 Vaccines and the Importance of Effective Vaccination Programs in Pandemic Times

Abstract

Since the worldwide COVID-19 pandemic was declared a year ago, the search for vaccines has become the top priority in order to restore normalcy after 2.5 million deaths worldwide, overloaded sanitary systems, and a huge economic burden. Vaccine development has represented a step towards the desired herd immunity in a short period of time, owing to a high level of investment, the focus of researchers, and the urge for the authorization of the faster administration of vaccines. Nevertheless, this objective may only be achieved by pursuing effective strategies and policies in various countries worldwide. In the present review, some aspects involved in accomplishing a successful vaccination program are addressed, in addition to the importance of vaccination in a pandemic in the face of unwillingness, conspiracy theories, or a lack of information among the public. Moreover, we provide some updated points related to the landscape of the clinical development of vaccine candidates, specifically, the top five vaccines that are already being assessed in Phase IV clinical trials (BNT162b2, mRNA-1273, AZD1222, Ad26.COV2.S, and CoronaVac).

Keywords: COVID-19; SARS-CoV-2; adenovirus-based vaccines; coronavirus; inactivated virus vaccines; mRNA vaccines; pandemic management; vaccination programs; vaccine acceptance; vaccine hesitancy.

Figure 1

The role of vaccines during the SARS-CoV-2 pandemic and the main concerns in the general population. The proper communication and exposition of the main concerns regarding vaccination are crucial for ending this global predicament.

Figure 2

Designs of, and immune reactions promoted by, COVID-19 vaccines. mRNA-based, adenoviral vectors, or inactivated virus can induce a coordinated innate and adaptive response, prominently limiting the damage caused by SARS-CoV-2 infection. In all cases, the recognition of the spike protein activates the innate immune system and interferon pathways, showing antiviral properties, promoting T and B cell responses, with an augmentation of cytolytic T cells and antibodies secreted against SARS-CoV-2.