Comprehensive narrative review of real-world COVID-19 vaccines: viewpoints and opportunities

Abstract

Currently, people all over the world have been affected by coronavirus disease 2019 (COVID-19). Fighting against COVID-19 is the top priority for all the countries and nations. The development of a safe and effective COVID-19 vaccine is considered the optimal way of ending the pandemic. Three hundred and 44 vaccines were in development, with 149 undergoing clinical research and 35 authorized for emergency use as to March 15 of 2022. Many studies have shown the effective role of COVID-19 vaccines in preventing SARS-CoV-2 infections as well as serious and fatal COVID-19 cases. However, tough challenges have arisen regarding COVID-19 vaccines, including long-term immunity, emerging COVID-19 variants, and vaccine inequalities. A systematic review was performed of recent COVID-19 vaccine studies, with a focus on vaccine type, efficacy and effectiveness, and protection against SARS-CoV-2 variants, breakthrough infections, safety, deployment and vaccine strategies used in the real-world. Ultimately, there is a need to establish a unified evaluation standard of vaccine effectiveness, monitor vaccine safety and effectiveness, along with the virological characteristics of SARS-CoV-2 variants; and determine the most useful booster schedule. These aspects must be coordinated to ensure timely responses to beneficial or detrimental situations. In the future, global efforts should be directed toward effective and immediate vaccine allocations, improving vaccine coverage, SARS-CoV-2 new variants tracking, and vaccine booster development.

Keywords: SARS-CoV-2 variants; breakthrough infection; coronavirus disease 2019; emergency use authorization; mass vaccine administration; vaccine type.

Figure 1:

Overview of COVID-19 vaccine development in clinical trials and approval phases.

Figure 2:

Landscape of COVID-19 vaccine candidates in clinical development and authorization across the globe March 15, 2022. Notes: A: A total of 344 vaccine candidates is in pre-clinical and clinical development. B: The percentages and number of different vaccine candidates’ in clinical development. C: The number of different vaccine candidates in clinical testing I-IV phase. Abbreviation: VVnr = Viral vector (No n-replicating); APC= Antigen Presenting Cell; VVr= Viral Vector (replicating); IV= Inactivated Virus; PS= Protein subunit; LAV= Live Attenuated Virus. VLP= virus-like particle; NA=no data available. The vaccine candidate data was sourced from WHO (https://www.who.int/publications/m/item/draft-landscape-of-covid-19-candidate-vaccines).

Figure 3:

Conceptual graph for four different COVID-19 vaccine types. Notes: A: Inactive vaccine; B: mRNA vaccine; C: Viral vector vaccine; D: Protein subunit vaccine.

Figure 4:

The differenct COVID-19 vaccine effectiveness of full immunization was assessed in real world study. Notes: A: mRNA vaccine; B: Adenoviral vector vaccine (non-replicating); C: Inactive vaccine. DI = Documented infection; SCOFD = Severe, critical or fatal disease; ICU = Intensive Care Unit.

Figure 5:

COVID-19 vaccine efficacy at preventing infection for SARS-CoV-2 variants Alpha, Beta, Gamma, and Delta.

Figure 6:

COVID-19 vaccine doses administered by country income group (March 16, 2022). Notes: Data from our world in data: https://ourworldindata.org/covid-vaccinations. The size of bubble represented the population of different countries, and the marked countries had the most people fully vaccinated per hundred at corresponding income levels.