A comprehensive review on COVID-19 vaccines: development, effectiveness, adverse effects, distribution and challenges

Abstract

The present SARS-CoV-2 induced COVID-19 pandemic is responsible for millions of deaths, illnesses, and economic loss worldwide. There are 21 COVID-19 vaccines from different platforms approved worldwide for emergency use until 13 August 2021. Later, BNT162b2 obtained full approval from the FDA. The efficacy of the leading vaccines such as BNT162b2, mRNA-1273, Gam-Covid-Vac, Ad26.COV2.S, ChAdOx1 nCoV-19, and BBIBP-CorV, against SARS-CoV-2 documented as 95%, 94.1%, 91.6%, 67%, 70.4%, and 78.1%, respectively. Moreover, against the Delta variant of SARS-CoV-2, BNT162b2, ChAdOx1 nCoV-19, and BBV152 showed 88%, 70%, and 65.2% efficacy, respectively. Apart from the common adverse effects such as fever, fatigue, headache, and pain in the injection site, Bell's palsy with BNT162b2, myocarditis and pericarditis with mRNA-1273, and thrombosis with ChAdOx1 nCoV-19 have been reported though seemed not alarming. Furthermore, global production and distribution of vaccines should be ensured in an equal and justifiable way that the immunity and protection against the virus would be optimum and persistent.

Keywords: Adverse effects; COVID-19 vaccines; Distribution; Effectiveness; Immunogenicity; SARS-CoV-2.

Fig. 1

Types of different COVID-19 vaccines and their manufacturing features. DNA vaccines manufacturing requires a plasmid DNA, but RNA vaccines are directly manufactured using lipid bilayer coatings; in both cases, the RNA of SARS-CoV-2 is the primarily targeted nucleic acid. For the inactivated and weakened vaccines, the original SARS-CoV-2 is inactivated or modified to retain antigenic properties but has no pathogenic phenomenon as the original SARS-CoV-2. The protein and virus-like particles vaccine manufacturing are similar as both target the surface proteins of the original SARS-CoV-2 without considering its nucleic acid properties. In viral vector vaccines, modified viral particles (vectors) which can be replicating or non-replicating in nature are used to deliver the original SARS-CoV-2 RNA into the host (The figure has been drawn by conceiving ideas from Dai et al. [39])

Fig. 2

An overview of COVID-19 vaccines’ ways of generating immunity against the SARS-CoV-2 in humans. All the vaccines have similarities in activating immune responses upon infection, introducing APC, and further antigen processing. Following antigen presentation by MHC class-II and MHC class-I of APC to CD4 + T cells and CD8 + T cells, respectively, activation of these cells occurs, which later provides both humoral and cellular immune responses. CD4 + T cells activation ensures B cells activation, subsequently activating plasma cells which provide antibodies as a means of the humoral response, while CD8 + T cells activation confirms cellular responses by providing active CD8 + T cells or cytotoxic T cells. All the vaccines are encountered directly to the APC except the mRNA, DNA, replicating vector, and weakened vaccines. The mRNA and DNA vaccines encode the desired protein upon cell entry, and then APC process and present these proteins to the immunological cells. Both the replicating vector and weakened vaccines have replicating abilities; thus, they replicate upon cellular entry and are further encountered by the APC in the same manner. Despite having similarities among the vaccine immune responses, the protein subunit, virus-like particle, non-replicating vector, and inactivated vaccines do not provide cellular immune responses as they have no cellular entry like the rest of the vaccines. Thus, mRNA, DNA, replicating vector, and weakened vaccines provide both humoral and cellular responses as they have cellular entry before the APC recognition (The figure has been drawn by conceiving ideas from Nature [90])

Fig. 3

A comparative overview of global vaccination coverage. People who received complete doses of any vaccines are considered in the figure. This map is created by Datawrapper (https://app.datawrapper.de/select/map) based on the data available at “https://ourworldindata.org/covid-vaccinations?country=OWID_WRL” on 14 August 2021. A total of 4.62 billion doses of vaccines were given to date, and 1.82 billion people worldwide became fully vaccinated