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Review
. 2021 Nov 24;9(12):1387.
doi: 10.3390/vaccines9121387.

A Systematic Review on COVID-19 Vaccine Strategies, Their Effectiveness, and Issues

Shahad Saif Khandker  1 , Brian Godman  2   3   4 , Md Irfan Jawad  5 , Bushra Ayat Meghla  5 , Taslima Akter Tisha  5 , Mohib Ullah Khondoker  1   6 , Md Ahsanul Haq  1 , Jaykaran Charan  7 , Ali Azam Talukder  5 , Nafisa Azmuda  5 , Shahana Sharmin  8 , Mohd Raeed Jamiruddin  1   8 , Mainul Haque  9 , Nihad Adnan  1   5
Affiliations
Review

A Systematic Review on COVID-19 Vaccine Strategies, Their Effectiveness, and Issues

Shahad Saif Khandker et al. Vaccines (Basel). .

Abstract

COVID-19 vaccines are indispensable, with the number of cases and mortality still rising, and currently no medicines are routinely available for reducing morbidity and mortality, apart from dexamethasone, although others are being trialed and launched. To date, only a limited number of vaccines have been given emergency use authorization by the US Food and Drug Administration and the European Medicines Agency. There is a need to systematically review the existing vaccine candidates and investigate their safety, efficacy, immunogenicity, unwanted events, and limitations. The review was undertaken by searching online databases, i.e., Google Scholar, PubMed, and ScienceDirect, with finally 59 studies selected. Our findings showed several types of vaccine candidates with different strategies against SARS-CoV-2, including inactivated, mRNA-based, recombinant, and nanoparticle-based vaccines, are being developed and launched. We have compared these vaccines in terms of their efficacy, side effects, and seroconversion based on data reported in the literature. We found mRNA vaccines appeared to have better efficacy, and inactivated ones had fewer side effects and similar seroconversion in all types of vaccines. Overall, global variant surveillance and systematic tweaking of vaccines, coupled with the evaluation and administering vaccines with the same or different technology in successive doses along with homologous and heterologous prime-booster strategy, have become essential to impede the pandemic. Their effectiveness appreciably outweighs any concerns with any adverse events.

Keywords: COVID-19 vaccines; clinical trials; inactivated vaccines; mRNA vaccines; nanoparticle-based vaccines; prime-booster strategy; recombinant vaccines; systematic review.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
A simplified PRISMA diagram of methodology. Primarily, a total of 869 articles were identified by our search strategy from different online databases (i.e., PubMed, ScienceDirect, and Google Scholar). From this, 755 articles were subsequently excluded due to ineligibility as they were case reports, review articles, correspondence, letters, or articles other than the original full-length article. From the remaining 114 articles, 16 articles were subsequently excluded as they did not match our study criteria (i.e., not related to SARS-CoV-2 vaccines). Ultimately, 59 articles were included for this systematic review after excluding duplicate articles (n = 39). Among the final 59 studies, 29 were clinical trials, and 30 were pre-clinical, non-clinical, or other original studies on vaccines. Quality assessments were undertaken for clinical trials.
Figure 2
Figure 2
Types of COVID-19 vaccine developed based on different technologies.
Figure 3
Figure 3
Efficacy of different SARS-CoV-2 vaccine candidates. Here, the small circles imply the reported efficacy after vaccination. All the data were extracted from the included articles, which were selected for this systematic review only. As all the vaccines did not have the same response levels, the 95% CIs were not evenly distributed. For BBIBP-CorV, we were not able to find the upper and lower limits of 95% CI; thus, it was not reported in the figure.
Figure 4
Figure 4
IgG seroconversion of several SARS-CoV-2 vaccines by trial Phase (i.e., Phase I/II/III), dose number (i.e., 1st or 2nd dose), or days after vaccination (i.e., day 14/28/29/42/56). Data were extracted from the included articles which were selected for this systematic review only.
Figure 5
Figure 5
Adverse effects (AE) of several SARS-CoV-2 vaccines by trial phase (i.e., Phase I/II/III), dose number (i.e., 1st or 2nd dose). Data were extracted from the included articles which were selected for this systematic review only.
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