Cited by 631SARS-CoV-2 and COVID-19 ResearchRNA Interference and Gene DeliverySARS-CoV-2 detection and testing

The DOI matches its Crossref record; 422 of the 422 references it cites were found in a registry or an index; 25 of the 299 sources its claims cite were checked for support.

Advances in COVID-19 mRNA vaccine development

Open access

Abstract

To date, the coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has determined 399,600,607 cases and 5,757,562 deaths worldwide. COVID-19 is a serious threat to human health globally. The World Health Organization (WHO) has declared COVID-19 pandemic a major public health emergency. Vaccination is the most effective and economical intervention for controlling the spread of epidemics, and consequently saving lives and protecting the health of the population. Various techniques have been employed in the development of COVID-19 vaccines. Among these, the COVID-19 messenger RNA (mRNA) vaccine has been drawing increasing attention owing to its great application prospects and advantages, which include short development cycle, easy industrialization, simple production process, flexibility to respond to new variants, and the capacity to induce better immune response. This review summarizes current knowledge on the structural characteristics, antigen design strategies, delivery systems, industrialization potential, quality control, latest clinical trials and real-world data of COVID-19 mRNA vaccines as well as mRNA technology. Current challenges and future directions in the development of preventive mRNA vaccines for major infectious diseases are also discussed.

Overview

AI snapshot

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TL;DR

This narrative review summarizes the structural design, antigen engineering, delivery systems, clinical trial results, and manufacturing/quality-control landscape of COVID-19 mRNA vaccines as of early 2022. It argues that mRNA platforms offer short development cycles, easy industrialization, and flexibility against new variants, while flagging ultra-cold-chain storage and long-term durability as open problems.

Key findings

  • As of February 8, 2022, WHO listed 337 COVID-19 vaccine candidates in development, of which 47 were mRNA vaccines and 23 had entered clinical trials.
  • BNT162b2 (30 μg, two doses 21 days apart) showed 95% efficacy against COVID-19 in individuals aged 16+, with efficacy of 91.3% over six months; a booster trial in over 5,000 people showed 95.6% protection. Real-world Qatar data showed effectiveness of 89.5% against Alpha, 75.0% against Beta, and 51.9% against Delta.
  • mRNA-1273 (100 μg, two doses 28 days apart) showed 94.1% efficacy in a phase III trial of 30,420 participants; real-world effectiveness was 100% against Alpha, 96.4% against Beta, and 73.1% against Delta, and 95.2% against Delta vs 62.5% against Omicron after three doses.
  • CureVac's CVnCoV (12 μg, unmodified nucleosides) showed only 48.2% overall efficacy and its rolling review was terminated by EMA; saRNA vaccines require far lower doses (0.1–10 μg) than mRNA-1273 (100 μg) or BNT162b2 (30 μg), but clinical seroconversion rates were incomplete (e.g., 8–61% for Imperial College London's LNP-nCoVsaRNA; ARCT-021 did not reach 100% seroconversion).
  • The mRNA vaccine production cycle from IVT to mRNA-LNP complex is approximately 10 days, with product potentially marketable within 40 days; storage requirements differ (mRNA-1273 six months at −20 °C; BNT162b2 six months at −60 to −80 °C; CVnCoV three months at −60 °C).

Methods

  • Design: narrative review of the literature on COVID-19 mRNA vaccine technology, covering mRNA types (non-replicating, saRNA, taRNA, circRNA), antigen design, delivery systems, clinical trials, production, and quality control.
  • Data: no primary data collection; the review synthesizes published preclinical studies, clinical trial registrations and results, real-world effectiveness data, and regulatory actions, with tables compiling UTR designs, antigen design strategies, and clinical trial candidates.
  • Analysis: descriptive synthesis; no meta-analysis or statistical pooling is reported.

Limitations

  • The paper does not state explicit limitations of its own review.
  • Evident from the text: this is a narrative (non-systematic) review with no stated search strategy, inclusion criteria, or risk-of-bias assessment, so selection of cited trials and real-world studies may be selective.
  • Evident from the text: clinical trial participant numbers and locations are noted as subject to change ("Clinical trials are regularly updated, therefore locations and the number of participants of clinical trials reported above are subjected to change"), and the review's data cut off in early 2022, predating later variant and durability data.

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Registry

Crossref · 10.1038/s41392-022-00950-y

Cites

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Statistics

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Figures

Fig. 1 Cellular and humoral immune responses induced by messenger RNA (mRNA) vaccine. mRNA delivered in an mRNA vaccine enters cells by endocytosis and, after release from the endosome, is translated into protein by ribosomes. Translated proteins can then activate the immune system primarily in two ways: i) proteins are degraded by the proteasome into peptides subsequently presented as antigens on the cell surface by major histocompatibility complex (MHC) class I molecules which bind to the T cell receptor (TCR) to activate CD8+ T cells to kill infected cells thorugh the secretion of perforin and granzyme; ii) proteins secreted extracellularly are engulfed by antigen-presenting cells (APCs) and degraded into peptides subsequently presented on the cell surface by MHC class II molecules for recognition by CD4+ T cells, which can activate both the cellular immune responses by secreting cytokines and the humoral immune responses by co-activating B cells. In addition, single-stranded RNA and double-stranded RNA delivered in mRNA vaccines bind to Toll-like receptor (TLR) in the endosome to activate the antiviral innate immune responses via the production of type-I interferon (IFN-I) which results in the induction of several IFN-1-stimulated genes involved in antiviral innate immunity, in a mechanism known as the self-adjuvant effect of a sequence-engineered mRNA. This figure is created with BioRender.com
Fig. 1 Cellular and humoral immune responses induced by messenger RNA (mRNA) vaccine. mRNA delivered in an mRNA vaccine enters cells by endocytosis and, after release from the endosome, is translated into protein by ribosomes. Translated proteins can then activate the immune system primarily in two ways: i) proteins are degraded by the proteasome into peptides subsequently presented as antigens on the cell surface by major histocompatibility complex (MHC) class I molecules which bind to the T cell receptor (TCR) to activate CD8+ T cells to kill infected cells thorugh the secretion of perforin and granzyme; ii) proteins secreted extracellularly are engulfed by antigen-presenting cells (APCs) and degraded into peptides subsequently presented on the cell surface by MHC class II molecules for recognition by CD4+ T cells, which can activate both the cellular immune responses by secreting cytokines and the humoral immune responses by co-activating B cells. In addition, single-stranded RNA and double-stranded RNA delivered in mRNA vaccines bind to Toll-like receptor (TLR) in the endosome to activate the antiviral innate immune responses via the production of type-I interferon (IFN-I) which results in the induction of several IFN-1-stimulated genes involved in antiviral innate immunity, in a mechanism known as the self-adjuvant effect of a sequence-engineered mRNA. This figure is created with BioRender.comCC BY · PubMed Central
Fig. 2 Proposed mechanism of endosomal escape of delivered mRNA. Endosomal escape of delivered mRNA is largely dependable on interactions between ionizable lipids and naturally occurring anionic phospholipids in the endosomal membrane.43 Prior to membrane fusion, ionizable lipids in lipid nanoparticles (LNPs) and anionic lipids in the endosomal membrane adopt a cylindrical conformation which is compatible with molecular packing in a bilayer phase. The acidic environment in endosomes facilitates protonation of ionizable lipids into cationic lipids. Cationic and anionic lipids generate ion pairs whose combined cross-sectional headgroup area is smaller than the total of individual headgroup areas before membrane fusion. Consequently, the ion pair adopts a conical shape which promotes the formation of inverted, non-bilayer phases, such as the hexagonal shape illustrated above. Thus, the formation of ion pairs between lipids promotes membrane fusion and disruption, allowing mRNA to escape from endosomes. This figure is created with BioRender.com
Fig. 2 Proposed mechanism of endosomal escape of delivered mRNA. Endosomal escape of delivered mRNA is largely dependable on interactions between ionizable lipids and naturally occurring anionic phospholipids in the endosomal membrane.43 Prior to membrane fusion, ionizable lipids in lipid nanoparticles (LNPs) and anionic lipids in the endosomal membrane adopt a cylindrical conformation which is compatible with molecular packing in a bilayer phase. The acidic environment in endosomes facilitates protonation of ionizable lipids into cationic lipids. Cationic and anionic lipids generate ion pairs whose combined cross-sectional headgroup area is smaller than the total of individual headgroup areas before membrane fusion. Consequently, the ion pair adopts a conical shape which promotes the formation of inverted, non-bilayer phases, such as the hexagonal shape illustrated above. Thus, the formation of ion pairs between lipids promotes membrane fusion and disruption, allowing mRNA to escape from endosomes. This figure is created with BioRender.comCC BY · PubMed Central
Fig. 3 Antigen expression in different types of mRNA vaccines. A The vaccine immunogen is encoded by a non-replicating RNA flanked by 5′ and 3′ UTRs (S protein). B Self-amplifying RNA (saRNA) encodes four nonstructural proteins (nsp 1–4) and a subgenomic promoter derived from the alphavirus genome. saRNA encodes a replicase and amplifies vaccine-encoding transcripts. C Trans-amplifying RNA (taRNA) uses two transcripts to enable self-amplification of replicase and the immunogen. D Circular RNA (circRNA) is circularized by the autocatalytic Group I ribozyme.223 The exon 2 is ligated upstream to exon 1, and a coding region is inserted between the exon-exon junction. During splicing, the 3′-OH of a guanosine nucleotide engages in a transesterification reaction at the 5′ splice site. The 5′ intron is excised, and the 3′-OH at the end of the intermediate engages in a second transesterification reaction at the 3′ splice site, resulting in the circularization of the immunogen mRNA. Upon entering the cell, the internal ribosome entry site (IRES) of circRNA initiates protein translation. The figures are created with BioRender.com
Fig. 3 Antigen expression in different types of mRNA vaccines. A The vaccine immunogen is encoded by a non-replicating RNA flanked by 5′ and 3′ UTRs (S protein). B Self-amplifying RNA (saRNA) encodes four nonstructural proteins (nsp 1–4) and a subgenomic promoter derived from the alphavirus genome. saRNA encodes a replicase and amplifies vaccine-encoding transcripts. C Trans-amplifying RNA (taRNA) uses two transcripts to enable self-amplification of replicase and the immunogen. D Circular RNA (circRNA) is circularized by the autocatalytic Group I ribozyme.223 The exon 2 is ligated upstream to exon 1, and a coding region is inserted between the exon-exon junction. During splicing, the 3′-OH of a guanosine nucleotide engages in a transesterification reaction at the 5′ splice site. The 5′ intron is excised, and the 3′-OH at the end of the intermediate engages in a second transesterification reaction at the 3′ splice site, resulting in the circularization of the immunogen mRNA. Upon entering the cell, the internal ribosome entry site (IRES) of circRNA initiates protein translation. The figures are created with BioRender.comCC BY · PubMed Central
Fig. 4 Structure of mRNA and nucleotide modifications. mRNA molecules are synthesized in vitro with a 5′-cap 1 structure and chemically modified nucleotides as substitutes for natural nucleotides, which enhances stability and translation efficiency of mRNA as well as reduces innate immune response. This figure is created with BioRender.com
Fig. 4 Structure of mRNA and nucleotide modifications. mRNA molecules are synthesized in vitro with a 5′-cap 1 structure and chemically modified nucleotides as substitutes for natural nucleotides, which enhances stability and translation efficiency of mRNA as well as reduces innate immune response. This figure is created with BioRender.comCC BY · PubMed Central
Fig. 5 mRNA capping procedure using capping enzymes or cap analogs. A Production of post-transcriptional modifications of mRNA with cap0 requires three enzymes: triphosphatase, guanylyltransferase, and N7-methyltransferase with S-adenosylmethionine (SAM) as the methyl donor. Subsequently, the cap0 is modified with 2′-O-ribose methyltransferase to generate the cap1 structure. B Cap analogs commonly used for in vitro transcription of mRNA are CleanCap® Reagent AG (TriLink) and CleanCap® Reagent AU (TriLink). The proposed mechanism of CleanCap co-transcriptional initiation involves the docking of AmG or AmU dimers onto the +1 and +2 positions in template nucleotides. Initiation occurs upon coupling of CleanCap with an nucleoside triphosphate (NTP) occupying the +3 position.157
Fig. 5 mRNA capping procedure using capping enzymes or cap analogs. A Production of post-transcriptional modifications of mRNA with cap0 requires three enzymes: triphosphatase, guanylyltransferase, and N7-methyltransferase with S-adenosylmethionine (SAM) as the methyl donor. Subsequently, the cap0 is modified with 2′-O-ribose methyltransferase to generate the cap1 structure. B Cap analogs commonly used for in vitro transcription of mRNA are CleanCap® Reagent AG (TriLink) and CleanCap® Reagent AU (TriLink). The proposed mechanism of CleanCap co-transcriptional initiation involves the docking of AmG or AmU dimers onto the +1 and +2 positions in template nucleotides. Initiation occurs upon coupling of CleanCap with an nucleoside triphosphate (NTP) occupying the +3 position.157CC BY · PubMed Central
Fig. 6 Rationale underlying the design strategy of COVID-19 mRNA vaccine. Representation of the SARS-CoV-2 reference genome showing structural, nonstructural, and accessory proteins, consisting of ORF1a, ORF1b, Spike protein (S), ORF3a, ORF3b, Envelope (E), Membrane (M), ORF6, ORF7a, ORF7b, ORF8, ORF9b, ORF14, Nucleocapsid (N) and ORF10.485 Spike and receptor-binding domain (RBD) proteins are mainly used as target antigens for the design and optimization of COVID-19 mRNA vaccines. This figure is created with BioRender.com
Fig. 6 Rationale underlying the design strategy of COVID-19 mRNA vaccine. Representation of the SARS-CoV-2 reference genome showing structural, nonstructural, and accessory proteins, consisting of ORF1a, ORF1b, Spike protein (S), ORF3a, ORF3b, Envelope (E), Membrane (M), ORF6, ORF7a, ORF7b, ORF8, ORF9b, ORF14, Nucleocapsid (N) and ORF10.485 Spike and receptor-binding domain (RBD) proteins are mainly used as target antigens for the design and optimization of COVID-19 mRNA vaccines. This figure is created with BioRender.comCC BY · PubMed Central
Fig. 7 Structure of lipid nanoparticles (LNPs) and lipid components employed in currently available COVID-19 mRNA vaccines. LNPs are composed of four components: ionizable lipid, helper lipid, cholesterol, and PEGylated lipid. Binding with mRNA occurs by the ionizable lipid that occupies the central core of the LNP. PEGylated lipid is found on the surface of LNPs along with helper lipid forming the bilayer. Cholesterol, charged ionizable lipids, and neutral ionizable lipids are distributed throughout LNPs. The confirmed or the most likely chemical structure of ionizable lipids employed in COVID-19 mRNA vaccines developed by Moderna, BioNTech, CureVac, Arcturus, Imperial College London, and Chulalongkorn University.289 *Molar lipid ratio (%) of ionizable lipid: helper lipid: cholesterol: PEGylated lipid; **NA: Not applicable
Fig. 7 Structure of lipid nanoparticles (LNPs) and lipid components employed in currently available COVID-19 mRNA vaccines. LNPs are composed of four components: ionizable lipid, helper lipid, cholesterol, and PEGylated lipid. Binding with mRNA occurs by the ionizable lipid that occupies the central core of the LNP. PEGylated lipid is found on the surface of LNPs along with helper lipid forming the bilayer. Cholesterol, charged ionizable lipids, and neutral ionizable lipids are distributed throughout LNPs. The confirmed or the most likely chemical structure of ionizable lipids employed in COVID-19 mRNA vaccines developed by Moderna, BioNTech, CureVac, Arcturus, Imperial College London, and Chulalongkorn University.289 *Molar lipid ratio (%) of ionizable lipid: helper lipid: cholesterol: PEGylated lipid; **NA: Not applicableCC BY · PubMed Central
Fig. 8 Production process of mRNA vaccines. The design of an mRNA vaccine is conditioned to the definition of the antigen sequence of the target pathogen. By determining the target antigen and optimizing its coding sequence, the mRNA can be transcribed in vitro by RNA polymerase. The synthesized mRNA is purified by different processes and then mixed with a lipid phase using microfluidics and encapsulated into an mRNA-lipid nanoparticle (mRNA-LNP) complex. Subsequently, self-assembly of LNPs is completed by dilution and concentration by ultrafiltration. Finally, after sterile filtration, filling, and capping, the mRNA vaccine is obtained
Fig. 8 Production process of mRNA vaccines. The design of an mRNA vaccine is conditioned to the definition of the antigen sequence of the target pathogen. By determining the target antigen and optimizing its coding sequence, the mRNA can be transcribed in vitro by RNA polymerase. The synthesized mRNA is purified by different processes and then mixed with a lipid phase using microfluidics and encapsulated into an mRNA-lipid nanoparticle (mRNA-LNP) complex. Subsequently, self-assembly of LNPs is completed by dilution and concentration by ultrafiltration. Finally, after sterile filtration, filling, and capping, the mRNA vaccine is obtainedCC BY · PubMed Central

Verification

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  • It may state two separate claims as one. 84
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  • The quote only partly states this claim. 1
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  • The paper relies on this without support.

    Vaccination is the most effective and economical intervention for controlling the spread of epidemics and saving lives.

    “Vaccination is the most effective and economical intervention for controlling the spread of epidemics, and consequently saving lives and protecting the health of the population.”
  • The paper relies on this without support.

    Currently, no specific drug has been identified for COVID-19 prevention or treatment.

    “Currently, no specific drug has been identified for COVID-19 prevention or treatment, and vaccination is the most economical and effective intervention to limit the spread of SARS-CoV-2.”
  • The paper relies on this without support.

    mRNA is a negatively charged and unstable molecule.

    “Since mRNA is a negatively charged and unstable molecule, it is generally encapsulated in a delivery vehicle in order to enter the target cell.”
  • The paper relies on this without support.

    Among 37 people who presented anaphylaxis after BNT162b2 vaccination, 57% had a history of allergy and four had a history of cosmetic allergy.

    “This is related to the fact 57% of the 37 people who presented anaphylaxis had a history of allergy, and four had a history of cosmetic allergy, suggesting a potential role for PEG in inducing anaphylaxis.”
  • The paper relies on this without support.

    The entire production cycle for an mRNA vaccine from IVT of mRNA to preparation of mRNA-LNP complexes might last approximately 10 days, and including qualification and release, the product can be available on the market within 40 days.

    “From IVT of mRNA to preparation of mRNA-LNP complexes, the entire production cycle for an mRNA vaccine might last approximately 10 days. Considering also the time required for qualification and release, the product can be available on the market within 40 days.”
  • The paper relies on this without support.

    mRNA vaccine technology is broadly compatible with any mRNA sequences and virtually all vaccines based on proteins can be produced using this technology.

    “As a technology platform, mRNA vaccine technology is broadly compatible with any mRNA sequences and virtually all vaccines based on proteins can be produced using this technology.”
  • The paper relies on this without support.

    mRNA is highly susceptible to degradation by ubiquitous RNases.

    “Studies showed that mRNA is highly susceptible to degradation by the ubiquitous RNases, therefore ultra-low temperature storage is recommended to limit RNase activity whilst ensuring mRNA stability effectively.”
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Citations

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Research works printed but not linked: 9

  1. Qu, L. et al. Circular RNA Vaccines against SARS-CoV-2 and Emerging Variants. BioRxiv, https://doi.org/10.1101/2021.03.16.435594 (2022). · DOI · Paper page
  2. Zhang, H. et al. Lineardesign: Efficient algorithms for optimized mrna sequence design. arXiv preprint arXiv:2004.10177, https://arxiv.org/abs/2004.10177 (2021). · arXiv
  3. Walsh, E. E. et al. Safety and Immunogenicity of Two RNA-Based Covid-19 Vaccine Candidates. N. Engl. J. Med 383, 2439–2450 (2020). · DOI · Paper page
  4. Burris, H. A. III et al. A phase 1, open-label, multicenter study to assess the safety, tolerability, and immunogenicity of mRNA-4157 alone in subjects with resected solid tumors and in combination with pembrolizumab in subjects with unresectable solid tumors (Keynote-603). J. Clin. Oncol. 37, 2523–2523 (2019). · DOI · Paper page
  5. Mulligan, M. J. et al. Phase I/II study of COVID-19 RNA vaccine BNT162b1 in adults. Nature 586, 589–593 (2020). · DOI · Paper page
  6. Pfizer and BioNTech receive authorization in the European Union for COVID-19 vaccine, https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-receive-authorization-european-union (2020).
  7. Pfizer. Pfizer and BioNTech announce Phase 3 trial data showing high efficacy of a booster dose of their COVID-19 vaccine, https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-announce-phase-3-trial-data-showing (2021).
  8. Sanofi to focus its COVID-19 development efforts on the recombinant vaccine candidate, https://www.sanofi.com/en/media-room/press-releases/2021/2021-09-28-18-44-47-2304800 (2021).
  9. Sanofi announces positive Phase 1/2 study interim results for its first mRNA-based vaccine candidate, https://www.sanofi.com/en/media-room/press-releases/2021/2021-09-28-08-00-00-2304069 (2021).

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Metadata

Authors
Fang, E., Liu, X., Li, M., Zhang, Z., Song, L., Zhu, B., Wu, X., Liu, J., Zhao, D., & Li, Y.
Affiliations
  • National Institutes for Food and Drug Control (CN)
  • Texas A&M University (US)
Corresponding author
Li, Yuhua
Venue
Signal Transduction and Targeted Therapy
Published
2022-03-23
Volume
7
Issue
1
Pages
94-94
ISSN
2059-3635 (ISSN-L)
OpenAlex
W4220852564
Cited by
601
References
415
Citations by year
2026: 81 · 2025: 158 · 2024: 186 · 2023: 134 · 2022: 42
FWCI
20.09
Type
journal article
Language
en
Open access
Locations
  • Signal Transduction and Targeted Therapy (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Topics
  • Health Sciences › Medicine › Infectious Diseases › SARS-CoV-2 and COVID-19 Research
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › RNA Interference and Gene Delivery
  • Health Sciences › Medicine › Infectious Diseases › SARS-CoV-2 detection and testing
Keywords
COVID-19 pandemic, SARS-CoV-2, mRNA vaccines, vaccine development, antigen design, mRNA delivery systems, vaccine quality control, clinical trials, real-world data, mRNA technology, prophylactic vaccines
MeSH terms
COVID-19, SARS-CoV-2, COVID-19 Vaccines, mRNA Vaccines, Humans, RNA, Messenger, Vaccines, Synthetic, Pandemics

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